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The Encyclopedia of Horology

Serial-number guide

Illinois Watch Company Serial Numbers

Partially verified

What a Illinois Watch Company serial number can establish, what it cannot, and how to record a date estimate another researcher could check.

Diagram

maker or gradeserialcase hallmarksimport and assay marks
Schematic: where markings are found. An outline schematic drawn to show the arrangement of the parts discussed here. It is not a dimensioned working drawing and does not depict a particular maker's calibre.

Method

Reading the number, step by step

  1. 1. Find the movement number

    American movements and cases were usually sold separately and cased by the retailer, so the case number belongs to the case maker's own sequence and cannot date the movement.

  2. 2. Understand what it encodes

    Illinois movement serials are broadly sequential and are used to look up an approximate production period and, more usefully, the grade, which determines jewels, adjustment and market.

  3. 3. Judge how precise the date can be

    Estimated: the result is an approximate batch year. Later production following the firm's acquisition by Hamilton should be checked in sources covering that period specifically.

  4. 4. Check the records behind the tables

    Collector-compiled serial and grade tables (for example those published through the NAWCC community and public lookup sites) are the usual reference; they are reconstructions, not facsimiles of complete factory ledgers.

Quick facts

Manufacturer
Illinois Watch Company
Dating confidence
Estimate only — see notes
Editorial status
Partially verified

Sources & references

  1. NAWCC published research on American watch companies
  2. Community serial/grade lookup compilations (secondary, approximate)

Where sources disagree, the disagreement is stated rather than resolved silently.

Limits

What the number does not prove

Questions

Frequently asked

Where is the serial number on a Illinois Watch Company watch?
American movements and cases were usually sold separately and cased by the retailer, so the case number belongs to the case maker's own sequence and cannot date the movement.
What do Illinois Watch Company serial numbers mean?
Illinois movement serials are broadly sequential and are used to look up an approximate production period and, more usefully, the grade, which determines jewels, adjustment and market.
How accurate is dating a Illinois Watch Company watch by serial number?
Estimated: the result is an approximate batch year. Later production following the firm's acquisition by Hamilton should be checked in sources covering that period specifically.
Where are Illinois Watch Company production records held?
Collector-compiled serial and grade tables (for example those published through the NAWCC community and public lookup sites) are the usual reference; they are reconstructions, not facsimiles of complete factory ledgers.

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