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 343 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 - 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 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 below.

• The presence of lower FAT numbers on movements exhibiting later configuration traits (three dial foot screws and 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 structural transition is suggested in Model 12 and Model 13 movements: earlier examples consistently exhibit two dial foot screws and a FAT number stamped on the back of the top plate, while later examples exhibit three dial foot screws and no rear top-plate FAT stamping. This 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.

• 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.