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The Encyclopedia of Horology

Pocket watch · Dust-proof pocket watch

Keystone Watch Co. Patent "Dust Proof" Pocket Watch, c. 1887

Partially verified

According to the Pocket Watch Database blog, this pocket watch dates to circa 1887 and was manufactured by the Keystone Watch Co. The movement is an 18-size design featuring gilt-damaskeened plates and 10 jewels. Its distinctive feature is a patented dust-proof windowed attachment covering the balance wheel, intended to seal the internal mechanism from outside debris. The watch incorporates Abraham Bitner's patent micrometric regulator alongside other patents granted during Bitner's tenure. Source documentation records that the movement is cased in a gold-filled Essex Watch Case Company case under the Standard trademark.

Macro photograph showing the dust-proof curved window, balance cock, and Bitner micrometric regulator on a Keystone Watch Co. movement
Macro photograph showing the dust-proof curved window, balance cock, and Bitner micrometric regulator on a Keystone Watch Co. movement — Nathan Moore / Pocket Watch Database. Rights pending — permission not yet requested. Original source

Catalogue identity

Source
blog.pocketwatchdatabase.com
Category
Pocket watch · Dust-proof pocket watch
Maker / attribution
Keystone Watch Co.
Reference
Not recorded
Catalogue / lot identifier
Source URL identifies the listing
Source-reported date
c. 1887
Country
United States

Source-reported attribution and specifications are not independent authentication. A listing does not establish present ownership, current display, availability or permission to reproduce.

Object description

Visible Balance Cock and Dust-Proof Construction

Macro examination of the movement reveals a specialized curved transparent window secured over the balance wheel opening adjacent to the balance cock. This construction corresponds directly to the patented design feature intended to enclose the balance assembly.

The adjacent movement plate displays gilt damaskeening and is engraved with the designation 'PAT. DUST PROOF.' alongside visible partial serial digits '570'. A steel micrometric regulator index arm extends over an engraved graduated scale, controlled by a threaded fine-adjustment screw mechanism, tension spring, and blued steel fastening screws. Along the outer margin, a hinged metallic case rim is visible.

Evidence for this section
  • “Curved transparent window covering the balance opening adjacent to the balance cock”
  • “Gilt-damaskeened movement plate engraved with 'PAT. DUST PROOF.' and partial serial digits '570'”
  • “Threaded fine-adjustment screw mechanism and tension spring fitted to the regulator arm”

Reported Movement and Patent Specifications

According to the source documentation, the movement is an 18-size, 10-jewel mechanism featuring gilt-damaskeened plates, assigned an estimated total production run noted as 'ETP ~7,400'. The dust-proof function relies on a 'windowed attachment covering the balance wheel – essentially “sealing” the mechanics of the watch from outside debris'.

The watch mechanism incorporates 'Abraham Bitner’s Patent Micrometric Regulator' along with several other patents granted to Bitner during his period of leadership at the Keystone factory. The movement is dated approximately to circa 1887 in the source title.

Evidence for this section
  • “18-Size, Gilt-Damaskeened Plates, 10 Jewels, ETP ~7,400.”
  • “windowed attachment covering the balance wheel – essentially “sealing” the mechanics of the watch from outside debris”
  • “Abraham Bitner’s Patent Micrometric Regulator”

Reported Casing, Hands, and Source Scope

The source documents that the complete watch was fitted with '“Keystone” shape gilt hands' and housed in a gold-filled case manufactured by the Essex Watch Case Company, marked under the '“Standard” name and trademark'. Furthermore, the source notes historical retail through the 'Atkinson Bros. company' in the late 1880s via watch clubs.

However, physical verification from the provided primary detail image is limited strictly to the balance cock, regulator, transparent window, and adjoining plate edge. The full dial layout, the complete serial number, the remainder of the movement, and the exterior of the Essex case are not depicted in this image and remain unverified by direct visual inspection.

Evidence for this section
  • “This watch is correctly fitted with “Keystone” shape gilt hands and is housed in a gold-filled case manufactured at the Essex Watch Case Company using the “Standard” name and trademark”
  • “In the late 1880s, the Atkinson Bros. company sold these as complete watches via various schemes, including the formation of watch clubs in major cities across the United States.”

Open research questions

  • What is the complete serial number stamped on the lower plate beneath the visible '570' digits?
  • Does the Essex Watch Case Company gold-filled case retain matching serial numbers or specific Standard trademark stamps on its inner cuvette?
  • What specific patent dates or patent numbers granted to Abraham Bitner are stamped elsewhere across the full movement bridge layout?

Source evidence

Recorded claims and source quotations for Keystone Watch Co. Patent "Dust Proof" Pocket Watch, c. 1887
FieldSource-reported valueSource quotation
Movement Size and Configuration18-Size, Gilt-Damaskeened Plates, 10 Jewels“18-Size, Gilt-Damaskeened Plates, 10 Jewels”
Regulator PatentAbraham Bitner's Patent Micrometric Regulator“Abraham Bitner’s Patent Micrometric Regulator”
Dust-Proof MechanismWindowed attachment covering the balance wheel“windowed attachment covering the balance wheel – essentially “sealing” the mechanics of the watch from outside debris”
Case ManufactureEssex Watch Case Company gold-filled case“housed in a gold-filled case manufactured at the Essex Watch Case Company using the “Standard” name and trademark”
Estimated Total ProductionApproximately 7,400“ETP ~7,400”
Hand Type"Keystone" shape gilt hands““Keystone” shape gilt hands”
Historical DistributorAtkinson Bros. company“Atkinson Bros. company sold these as complete watches via various schemes”

Visible details

  • Curved transparent window covering the balance opening adjacent to the balance cock
  • Gilt-damaskeened movement plate engraved with 'PAT. DUST PROOF.' and partial serial digits '570'
  • Steel micrometric regulator index arm positioned over a graduated scale
  • Threaded fine-adjustment screw mechanism and tension spring fitted to the regulator arm
  • Blued steel screws securing regulator components on the balance cock
  • Hinged metallic case rim visible along the left margin

Research qualifications

  • Full dial, entire movement layout, and case exterior are not depicted in this macro detail view
  • Only trailing digits of the serial number are visible on the plate edge

Photograph identity and source facts were screened before import; rights clearance remains pending.

Consulted source

c.1887 Keystone Watch Co. Patent "Dust Proof" Watch - 18-Size, Gilt-Damaskeened Plates, 10 Jewels - Pocket Watch Database Blog

Reviewed 2026-10-21 · Record f2823f4e10

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Glossary explanations for terms named in this object’s record.