FAT Numbers

Factory Assigned Tracking Numbers

for Century Grade Movement Components

Introductory Information & Model 10

Model 11

Model 12

Model 13 & Evidence Summary

1904 Seth Thomas Watch Material Catalog No. 650

An examination of seventy-two Seth Thomas Model 10 – Model 13 pocket watch movements having no serial numbers on the top plates has been undertaken and is documented here. All known Seth Thomas Model 10-13 movements are private label movements, which contributes an article of individual identity beyond model number to each movement.

Sample Distribution by Model and Private Label (N = 72)

Model 10 Model 11 Model 12 Model 13 Totals

‍ ‍Athabasca = 0 Athabasca = 0 Athabasca = 3 Athabasca = 0 ‍ ‍3

‍ ‍Century USA = 5 Century USA = 8 Century USA = 11 Century USA = 12‍ ‍36

‍ ‍Colonial USA = 0 Colonial USA = 0 Colonial USA = 1 Colonial USA = 0‍ ‍1

‍ ‍Corona Watch Co. = 2 Corona Watch Co. = 0 Corona Watch Co. = 6 Corona Watch Co. = 4‍ ‍12

‍ ‍Edgemere = 0 Edgemere = 0 Edgemere = 2 Edgemere = 3‍ ‍5

‍ ‍Pan-American = 3 Pan-American = 4 Pan-American = 0 Pan-American = 0‍ ‍7

‍ ‍Republic USA = 0 Republic USA = 0 Republic USA = 2 Republic USA = 1‍ ‍3

‍ ‍Rex = 0 Rex = 0 Rex = 0 Rex = 1 ‍ ‍1

‍ ‍Trainmens Special = 0 Trainmens Special = 0 Trainmens Special = 3 Trainmens Special = 1 ‍ ‍4

‍ Totals 10 12 28 22 72

View individual private label entries: Athabasca, Century USA, Corona Watch Co, Edgemere, Pan-American, Republic USA, Rex, Trainmens Special.

These non-numbered 18-size Century-grade pocket watch movements each carry a Factory Assigned Tracking Number (FAT Number) stamped on two to four of the following locations, the pillar plate, back of the top plate, underside of the balance bridge, and block style winding bridge.

Data shows that the FAT Number stamped on the pillar plate has not been omitted on any of the specimens examined. The FAT Number on the reverse side of the top plate, when present, has been exactly the same as the FAT Number shown on the pillar plate, the only exception observed to date being cases in which one of the plates appears to have been transplanted from another movement. Transplanted parts seem to be identified quite easily on the non-numbered Century grade movements using the FAT Numbers.

The FAT Numbers appearing on other parts of the movement, underside of the balance bridge and on the winding bridge, are frequently truncated showing the last three, two, or one digits of the FAT Number. The truncation of FAT Numbers across movement components mirrors established serial-number marking practices and does not, in itself, indicate a different functional purpose.

Since the pillar plate appears to be the most consistent and reliable source of the full Fat Number, the number appearing there is being observed as the FAT Number for any given movement.

Because each movement can be characterized by its factory production model, retail private label name, and factory assigned tracking number (FAT Number), these non-numbered movements possess sufficient structural identifiers to permit systematic documentation and the development of derived identifiers. The FAT Number Derived Identifier is comprised of the physical movement’s two-digit model number, the private label name, and the FAT Number found on the pillar plate of the movement.

It has been decided that tracking the number of dial feet screws tapped into the outer perimeter of the pillar plate is relevant for tracking the possible temporal aspect of data as we know that early Seth Thomas movements had only two dial feet screws where movements produced later were equipped with three dial feet screws to provide greater stability for the dial.

The “Ser#’s” displayed in this section’s images were assigned upon acquisition for internal collection tracking purposes and do not represent factory-applied serial numbers. They were also used when uploading the movements’ data to the Pocket Watch Database.

For the purpose of examining individual movement specimens, this reference illustrates the dial foot screw (DFS) location patterns used throughout the documentation images and provides a standardized reference for recording DFS count during specimen documentation. A dial foot screw (DFS) is located on outer perimeter of the pillar plate distal to the penetration for each dial foot.

No surviving factory documentation describing these markings has yet been identified; all conclusions presented here are based on physical examination and comparative analysis.

In the Seth Thomas Fan collection, FAT numbers observed on Model 10 movements range from 240 to 922. FAT numbers observed on Model 11 movements range from 116 to 34,301. FAT numbers observed on Model 12 movements range from 340 to 67,010. FAT numbers observed on Model 13 movements range from 182 to 324,601. Current evidence suggests FAT numbers may be unique within a model, but the factory’s full assignment logic is not yet known. These stamped numbers are illustrated and cataloged in the sections below.

The Complete Dataset - Private Label Progression, The Complete Dataset - Standard Sort and The Complete Dataset - Manufacturing Practices Sort can each be viewed in a separate tab.

Practical Use of FAT# Derived Identifiers

Independent of any factory-intent interpretation, FAT# Derived Identifiers provide a reliable means of distinguishing otherwise indistinguishable non-numbered Century movements that are visually similar in engraving, dial, and private-label configuration, making positive re-identification difficult once movements are removed from cases or long-term storage. FAT# Derived Identifiers are not serial numbers; but in practice, they function as serial-number equivalents to facilitate collection management and documentation for collectors working with these non-serialized movements. Naming is what turns objects into data points. The FAT# Derived Identifier is comprised of a two-digit model number, the private label name, and the FAT Number found on the pillar plate of the physical movement.

FAT Numbers possibly hold potential to assist horologists in the development of a deeper understanding of the production process and chronology that took place at the Seth Thomas factory while non-numbered Century grade movements were being produced.

The first test of the usefulness of FAT Numbers will be the development of a FAT# Derived Identifier for each non-numbered Century grade movement in the Seth Thomas Fan Collection. This part of the project holds the potential to create viable identifiers tied to physical non-numbered movements. If successful; this means that FAT Numbers will be proven able to play a role in assigning persistent identifiers to otherwise undistinguishable horological artifacts in a large collection.

Early Observations and Initial Inferences

A possible structural transition in top-plate marking and dial-foot configuration is observable within the dataset and is discussed in detail in the Evidence Summary section at the end of the Model 13 FAT Numbers page.

The presence of lower FAT numbers on movements exhibiting later configuration traits (three dial foot screws and/or absence of a FAT number on the back of the top plate) suggests that FAT numbers should not presently be interpreted as strictly chronological indicators.

A possible structural transition is suggested in Model 12 and Model 13 movements: examples exhibiting earlier configuration traits (FAT number on the back of the top plate and/or two dial feet screws) when contrasted with examples exhibiting later configuration traits (three dial foot screws and no rear top-plate FAT stamping). The later configuration aligns with the mechanical and marking practices seen in early numbered production, where the serial number appears on the front of the top plate.

Current evidence raises the possibility that elimination of rear-top-plate FAT stamping coincided with the factory’s reorganization of marking practices during the transition to numbered movements, though the precise sequencing of these changes (whether simultaneous or staged) remains under investigation.

Present data do not support interpreting FAT numbers as a simple ordinal production sequence across all Century-grade models. Whether FAT numbers correlate to production sequencing within specific models or configuration phases remains an open question pending additional documentation.

The omission of outward-facing identifiers in documented factory shipping materials suggests that Century-grade movements were distributed within a standardized, size-and-grade-based framework that did not require individual serial numbering. The presence of FAT# markings on such movements may indicate one possible internal method of differentiation operating independently of external identification.

Seth Thomas Watch Factory Tins & Cardboard Movement Holders

Factory Packaging and Distribution Context

Finished Seth Thomas movements were placed into soft cardboard movement holders immediately after production to protect their finish, and these holders were then nested within hard metal tins to prevent crushing during storage and transport. The information applied to these holders typically included size, jewel count, grade, and—in many documented cases—a serial number or production identifier written or stamped in a designated field.

The open-face Century example illustrated above differs in a notable way. While it clearly identifies size (“18 Size”), configuration (“Open Face”), grade (“Century”), and jewel count (“7 Jewel”), it provides no designated space for a serial number or other unique identifier. This omission is consistent with observed examples of non-numbered Century-grade movements.

Additional factory material supports the conclusion that this omission was intentional rather than accidental. Contemporary Seth Thomas mainspring packaging and parts charts show a highly standardized system of size-based classification and distribution. Where tracking or identification was required, space was explicitly provided for it. Where it was not required, it was omitted.

While packaging materials do not directly document factory tracking systems, they provide consistent contextual support, particularly when considered alongside non-numbered movements lacking serial identifiers.

The absence of both a factory signature on the cardboard holder and a serial number on associated Century-grade movements appears to reflect an intentional distribution practice rather than an omission or oversight. By the time of Model 10–13 production, Seth Thomas had already established mature private label and identification systems. The consistent omission of outward-facing identifiers in this context suggests that Century-grade movements were distributed within a standardized, size-and-grade-based framework that did not require individual serial numbering. The presence of FAT# markings on such movements may indicate an internal method of differentiation operating independently of external identification.

This more robust holder appears to represent a variation in packaging format rather than a departure from the standardized size- and grade-based distribution system observed across other examples.

Factory mainspring packaging demonstrating standardized size-based distribution with designated fields for required information. The original “Seth Thomas Watch Main Springs” label has been crossed out and replaced with handwritten size and number information, indicating that the box was repurposed to hold mainsprings of a different specification than originally supplied.

Additional data from other collections may clarify whether FAT numbers reflect batch assignment, model-scoped numbering, tooling sequences, or other internal factory processes.

Image Contribution Form

If you have previously documented a non-numbered Century-grade Model 10–13 movement and would like to contribute photographs for research purposes, this Image Contribution Form may be used.

NOTE: This page is under active development. It will continue to be updated as photographic documentation becomes available and as additional movements are added to the collection and documented. The research and classifications on this page follow the methods described in the Research Methodology.

In the illustrations below, the original Seth Thomas Fan Collection serial identifier is retained. Where present, a green alphanumeric label indicates a FAT Number–Derived Identifier used for internal cataloging and analysis. It is comprised of a two-digit model number, the private label name, and the FAT Number found on the pillar plate of the physical movement.

The following terms used within the illustrations below to qualify each FAT Number datapoint are defined, based on physical examination and comparative analysis, as follows: Original = No evidence of transplant observed. Transplant = Evidence strongly supports component transplant.