Evidence Summary

FAT Number Uniqueness Within the Dataset

Within the current dataset, duplication of pillar plate FAT numbers is observed across models (e.g., 11CENTURY182 and 13CORONA182). No duplication has yet been observed within a single model grouping.

These observations indicate that FAT numbers are not universally unique across all non-numbered Century-grade movements, while leaving open the possibility that they may be unique within individual models pending further data.

Configuration-Based Distinctions Observed Within the Dataset

Observed specimens group into distinct configuration patterns:

Model 10 and Model 11 (Century Old Model):

• Two dial foot screws

• FAT numbers stamped on pillar plate, balance bridge, and back of top plate

• No serial number

Model 12 and Model 13 (Century New Model):

• Three dial foot screws

• No rear top-plate FAT stamping

• Configuration consistent with early numbered production

Private labels such as Pan-American appear only within Model 10 and Model 11 in the current dataset and are therefore representative of Century Old Model production.

Transitional Configurations

Certain private labels (Century U.S.A., Colonial U.S.A., and Corona Watch Co.) appear in both Old Model (10–11) and New Model (12–13) groupings and exhibit transitional characteristics, including:

• Presence and subsequent absence of rear top-plate FAT stamping

• Coexistence of two- and three-dial-foot configurations

Within the current sample of early private-label specimens originally produced with two dial foot screws, the absence of rear top-plate stamping is already common, while the adoption of three dial foot screws remains comparatively rare.

This distribution suggests that the elimination of rear top-plate FAT stamping preceded the widespread adoption of the three dial foot screw configuration, though the precise sequencing of these changes remains unresolved.

Numerical Relationships Across Models

Numerically close pillar plate FAT numbers are observed across model pairs sharing the same movement orientation (e.g., open-face Models 10 and 12; hunting-case Models 11 and 13), rather than strictly within Old Model or New Model groupings.

This pattern suggests that internal numbering practices may have continued across the transition between Old and New Century models within orientation-based production streams.

These observations are based solely on the current dataset and should not be interpreted as definitive production sequencing.

Packaging and Distribution Context

Documented factory packaging and distribution materials show a consistent omission of outward-facing identifiers in examples of Century-grade movements.

These materials indicate that such movements were handled within a standardized, size- and grade-based distribution system that did not require individual serial numbering at the packaging stage.

Within this context, FAT markings may represent an internal method of differentiation operating independently of external identification systems.

Exploration / Examination of Numbered Century New Model Movements

Inspection of 41 numbered Model 12 movements (serial range 1001754–1300196, plus one higher example at 4068501) and 12 numbered Model 13 movements (serial range 1705002–1776870) shows:

• All exhibit three dial foot screws

• None retain rear top-plate FAT stamping

Inspection of non-numbered Model 12 and Model 13 movements shows a corresponding structural shift from:

• Two dial foot screws with rear top-plate FAT stamping
  to

• Three dial foot screws without rear top-plate FAT stamping

This establishes a clear structural transition within Model 12 and Model 13 production. The weaker transitional signal in Model 12 may reflect the substantially larger apparent surviving population of non-numbered Model 12 movements, within which late transitional configurations represent only a small proportion. By contrast, Model 13 may preserve a higher relative concentration of such late non-numbered examples.

Interpretation Limits

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, configuration phases, or internal factory processes remains an open question pending additional documentation.