A curated selection of antique scientific instruments and watchmaking tools at the intersection of optics and horology. The collection focuses on late 19th and early 20th century precision instruments used in optical and horological workshops: compound microscopes, watchmaker's measuring microscopes, spherometers and microscope accessories, including Swiss patent gauges and signed British optical work.
Most pieces in the current collection descend through the Thomas Guenther Collection, with earlier Egon Guenther provenance noted where present. For the wider identification framework, see the antique scientific instruments guide.
Ships worldwide from the Netherlands. Private viewings available by appointment.
The collection focuses on precision instruments used at the optical and horological bench in the late Victorian and Edwardian period. Four object types are represented in current stock: compound microscopes by named British optical makers, watchmaker's measuring microscopes with sliding stages, spherometers for curvature measurement, and coverslip micrometers for microscopy support. Each piece is offered as a working tool with documented provenance, not a decorative imitation of one.
About this collectionWhat's currently held and what's added next
The page is built around the four current pieces and is structured to flex as stock expands into adjacent object types — further microscopes by signed British, French and German makers; additional Swiss and Continental measuring instruments; watchmaker's lathes, staking and jeweling tools; meteorological and surveying instruments; drawing sets — as they arrive. Items are added only when maker, period and provenance can be documented.
Type
Maker / patent
Period
Notable detail
Compound microscope
R. & J. Beck Ltd. London
Late 19th – early 20th century
Serial 21696, fitted wooden case (lock missing, disclosed)
Watchmaker's measuring microscope
Continental European (unsigned)
Early 20th century
Brass optical assembly on cast iron base, sliding stage, calibrated scale
Spherometer
"Jauge Patent" (Swiss)
Early 20th century
Patent No. 28680, Swiss cross, cast and machined steel, weighted base
Coverslip micrometer
Unsigned (English laboratory)
c. 1880–1900
Brass body, lever-operated knife jaw, 0–360° enamel dial under glass
Typology · MicroscopesCompound microscopes and the British optical trade
Brass compound microscopes are one of the most documented sub-categories of antique scientific instruments. Britain produced a sustained run of high-quality optical firms across the second half of the 19th century, and London was the centre of the trade. R. & J. Beck Ltd. is one of the most recognised London makers, growing out of the partnership of Smith, Beck & Beck (later Smith & Beck, then R. & J. Beck Ltd. from 1865), working from City of London addresses and later from the Lister Works in Kentish Town. Joseph Beck wrote one of the standard period treatises on microscope construction, and the firm supplied microscopes for educational, medical and research use into the 20th century. Beck serial numbers can be approximately dated against published lists; serial 21696 sits in the late 19th to early 20th century range.
Points to assess on any cased Beck or contemporary compound microscope:
Maker mark and serial. Engraved "R. & J. Beck Ltd. London" on the tube or limb, with serial number on the foot or limb. The serial number lets the instrument be approximately dated and gives a long-tail SERP of its own.
Original lacquer. Warm uneven gold colour, with light wear on focus knobs and case-corner contact points. A re-lacquered instrument looks cold, bright and uniform — a common value-killer.
Optics. Objectives clean inside and out, free of fungus and balsam separation. Eyepieces with original diaphragms, lenses chip-free.
Case. Fitted wooden case, key (where the lock is present), original objectives in canisters, eyepieces and any small accessories.
For deeper coverage of the microscope sub-category see the antique microscopes sub-silo.
Typology · Watchmaker's MicroscopesMeasuring microscopes for the horological bench
A watchmaker's measuring microscope is a specific type of bench instrument that combines an optical microscope with a calibrated measuring stage. It is the predecessor of the 20th century toolmaker's microscope and was used in horological workshops to inspect and measure components too small to gauge accurately by hand: pivots, wheel teeth, escapement components, jewel holes, balance components.
The arrangement is straightforward in principle. A small inspection microscope is mounted on an adjustable head over a stage that slides on a precision way along a calibrated scale. A clamping fixture holds the workpiece. The horologist views the part through the eyepiece, brings a feature into the crosshair or graticule, advances the stage by a measured distance and reads off the displacement. The scale typically resolves to fractions of a millimetre.
Continental European examples from the late 19th and early 20th century are often unsigned, with the maker mark on a small label or stamped on a less visible surface. This does not reduce their value as working tools, though signed examples carry a premium. The category sits between general scientific microscopy and dedicated horological tooling, which is why these instruments often appear in both collector communities. They remain the most reliable way to measure very small geometric features under controlled magnification — see the horological antiques sub-silo for related bench equipment.
Typology · SpherometersCurvature measurement in optical and horological work
A spherometer measures the radius of curvature of a spherical or curved surface. The mechanism is a finely threaded central spindle that descends from a fixed three-legged frame. The legs sit on the surface being measured, the spindle is brought down to the same surface, and the calibrated reading on the spindle (combined with the known leg spacing) gives the curvature.
The instrument was developed for optical workshops, where lens curvature must be controlled to fractions of a millimetre, but it was adopted in any precision trade where a curved surface needed to be checked or matched. In horology specifically, spherometers were used for watch crystal curvature matching to bezels and cases, domed dial and hand surfaces in higher-grade work, balance wheel arms and rim profiles where curvature affected weight distribution and aerodynamics, and jewel setting profile in shock-protected or domed jewel work.
Patent or maker mark. "Jauge Patent" is a recognised Swiss precision-tool mark; combined with the Swiss cross and patent number it dates and authenticates the piece.
Spindle action. The threaded spindle should turn smoothly with no play or stiffness. Damaged or worn threads are the main failure mode.
Calibrated scale. Engraved numbering should be legible. Worn or partly polished-out engraving reduces both function and value.
Base. Heavy cast or machined steel base, ideally weighted, sometimes with cork or felt feet to protect the work surface.
Typology · Coverslip MicrometersMicroscope accessories for accurate objective correction
A coverslip micrometer (or coverslip thickness gauge) measures the thickness of the thin glass coverslip used to cover specimens on a microscope slide. This matters because the corrected achromatic and apochromatic objectives used in 19th and 20th century microscopy were designed for a specific coverslip thickness (usually 0.17 mm, sometimes 0.18 mm). A coverslip outside that range introduces spherical aberration and degrades image quality. Serious laboratory microscopy required coverslips to be measured before use.
A typical late Victorian coverslip micrometer is a brass instrument with a four-footed base, a lever-operated knife jaw that closes onto the coverslip, and a fine chain mechanism transmitting movement to a 0–360° enamel dial under glass. Sensitivity comes from the geared transmission: a small jaw movement produces a large, easily-read dial deflection. Construction is brass throughout, with the enamel dial and glass cover being the most fragile parts. Unsigned attribution is normal for this category — many fine instruments of this type were produced by small workshops supplying named retailers and are signed only on the case label, if at all. For the wider sub-silo see antique measuring instruments.
MaterialsLacquered brass, machined steel, cast iron and enamel
The instruments in the current collection are built from a small number of material families, each with its own assessment criteria.
Lacquered brass. Used for the optical assemblies of the Beck microscope and the watchmaker's measuring microscope, and for the body and base of the coverslip micrometer. Original 19th and early 20th century lacquer has a warm, uneven gold colour with small areas of wear on contact points (focus knobs, edges, feet). Re-lacquered brass looks cold, bright and uniform, often with visible drip marks at thread shoulders or where lacquer pooled.
Cast and machined steel. Used for the spherometer body and base. Original surface finishes (light blueing, straw temper colour, bare-machined surfaces with light oxidation patina) are dating and authenticity signals. Wire-wheel cleaning that produces a uniform bright finish damages both appearance and the surface hardness underneath.
Cast iron. Used for the heavy base of the watchmaker's measuring microscope. Cast iron bases were typically painted in maker's grey or black. Original paint, even with chips and edge wear, is preferred to a respray.
Enamel and glass. The coverslip micrometer's dial is vitreous enamel under a glass cover. Both are fragile. A clean, intact original dial is significantly more valuable than a repaired or replaced one.
Wood and case linings. The Beck microscope is accompanied by its fitted wooden storage case (lock missing). Original cases with their fitting blocks, linings and labels add substantially to value, even when the lock or external hardware is incomplete.
A re-lacquered instrument looks cold, bright and uniform. This is a common value-killer.
ProvenanceThomas Guenther and Egon Guenther
All four instruments in the current collection descend from the Thomas Guenther Collection. The Beck compound microscope additionally has earlier provenance from the Egon Guenther Collection by family descent.
Where named-collection provenance is documented, it is stated openly. Where it is not, no claim is implied.
CareDisplay, working use and what to avoid
These instruments survive indefinitely under the right conditions. The rules are simple and mostly about avoiding damage.
Do not polish brass with metal polish. Original lacquer and original patina are significant value factors. A soft dry brush and an occasional wipe with a barely-damp soft cloth is all that is required.
Do not clean optical elements. The Beck microscope objectives, the eyepieces of the watchmaker's measuring microscope and any glass elsewhere in the collection should be left alone unless they are demonstrably dirty in a way that affects use, and then only by a specialist.
Avoid direct sunlight and damp. UV damages case linings and ages lacquer; damp corrodes steel and lifts wood veneer.
Keep cases closed. The Beck microscope's fitted wooden case is part of the object; leaving it open exposes the linings to light and the brass to dust.
For working use. The watchmaker's measuring microscope and the spherometer can be used for their original function. Light clock or instrument oil on moving surfaces; never modern synthetic greases that harden over time.
Where an instrument is offered as a display piece rather than for working use, this is stated. None of the items in current stock are sold as display-only.
BuyingHow pieces are documented and sold
Every instrument is documented with maker where signed (R. & J. Beck Ltd., Jauge Patent), serial or patent number where present (Beck 21696, Jauge Patent 28680), approximate period or date range, material and construction, completeness of fittings and case, condition notes, and provenance where known. Originals are distinguished from later production copies and decorative reproduction work. Private viewings are available in the Netherlands by appointment, and worldwide shipping is arranged on request. Additional photographs, signature close-ups, mechanism detail shots and short video of moving parts are available before purchase.
Worldwide shipping from the Netherlands. Private viewings by appointment. Maker close-ups, serial numbers, mechanism detail shots and short video of moving parts available on request.
FAQFrequently asked questions about antique scientific instruments
What is in the current Scientific & Watchmaking Tools collection?
The collection currently holds four precision instruments at the optical and horological intersection: a R. & J. Beck Ltd. compound microscope (serial 21696, late 19th to early 20th century, with fitted wooden case); a Swiss Jauge Patent spherometer (number 28680, early 20th century, cast and machined steel); a watchmaker's measuring microscope with sliding stage (early 20th century, brass on cast iron base, Continental European); and a late Victorian brass coverslip micrometer (circa 1880-1900). All four descend from the Thomas Guenther Collection.
Who were R. & J. Beck Ltd.?
R. & J. Beck Ltd. were one of the leading London optical instrument makers of the late 19th and early 20th century. The firm grew out of the partnership of Smith, Beck & Beck (later Smith & Beck, then R. & J. Beck Ltd. from 1865), worked from City of London addresses and later from the Lister Works in Kentish Town, and supplied microscopes for educational, medical and research use. Joseph Beck wrote one of the standard period treatises on microscope construction. Beck serial numbers can be approximately dated against published lists.
What is a spherometer used for?
A spherometer measures the radius of curvature of a curved surface. It is built around a finely threaded central spindle in a three-legged frame: the legs sit on the surface, the spindle descends to the same surface, and the calibrated reading gives the curvature. Spherometers were developed for optical workshops (lens curvature) and adopted in horology for watch crystals, domed dial and hand surfaces, balance wheel profiles and jewel setting work. The Jauge Patent mark is a Swiss precision-tool patent name.
What is a watchmaker's measuring microscope?
A watchmaker's measuring microscope combines an optical inspection microscope with a calibrated sliding stage. The horologist views a small component through the eyepiece, brings a feature into a graticule or crosshair, advances the stage by a measured distance and reads the displacement off the scale. The instruments were used to measure pivots, wheel teeth, escapement components and jewel holes — small geometric features that cannot be gauged accurately by hand. They are predecessors to the 20th century toolmaker's microscope.
What is a coverslip micrometer?
A coverslip micrometer is a microscopy accessory that measures the thickness of the thin glass coverslip used over a specimen on a microscope slide. It matters because corrected microscope objectives are designed for a specific coverslip thickness (usually 0.17 mm); a thicker or thinner coverslip introduces spherical aberration. The typical instrument is a brass device with a lever-operated knife jaw and a chain-driven dial that gives a sensitive reading of jaw deflection. The example in the current collection has a 0–360 degree enamel dial under glass.
Should the brass on these instruments be polished?
No. Original lacquer and original patina on brass are significant value factors. Metal polish strips lacquer and produces a cold, uniform bright finish that informed buyers recognise immediately. Dust with a soft dry brush; an occasional wipe with a barely-damp soft cloth is all that is required. The same logic applies to the steel surfaces of the spherometer: leave them alone.
What is the Thomas Guenther and Egon Guenther provenance?
All four instruments in the current collection descend from the Thomas Guenther Collection. The R. & J. Beck microscope additionally has earlier provenance from the Egon Guenther Collection, by family descent to the Thomas Guenther Collection. Where named-collection provenance is documented, it is stated openly on the product page; the related Egon Guenther Collection is linked for context.
Are these instruments still usable, or are they for display?
The watchmaker's measuring microscope and the spherometer can be used for their original function and are offered with that in mind. The R. & J. Beck compound microscope can perform basic microscopy at moderate magnifications; serious modern microscopy is better served by modern objectives. The coverslip micrometer is functional but most often acquired as a documented historical object rather than a working tool. None of the items in the current collection are sold as display-only.
Do you ship internationally?
Yes. Esteemed Antiques ships worldwide from the Netherlands. Each instrument is packed in a purpose-prepared crate, with the original fitted case used as the inner container where it is part of the object (the Beck microscope's fitted wooden case is an example). Fully insured shipping and customs documentation are arranged on request.
