Seth Thomas Top Plates
Seth Thomas pocket watch movements evolved from very plain gilt plates, to intricately engraved nickel top and pillar plates, to eye grabbing two-tone and gilt damaskeened plates.
Seth Thomas Top Plates
The top plate is the plate located on the opposite side of the movement from the dial of a pocket watch. It might be referred to as the back of the movement, or as the mechanism because when the movement is in a pocket watch case, you would open the back cover of the watch case to see the top plate, which often is where you can see gears, pinions, and wheels, hence the mechanism reference.
Upper (“Northern”) Landmarks
Most of the Seth Thomas pocket watch models have a 3/4 top plate. The “cutout” is the 1/4 portion of the top plate that is missing on a 3/4 plate. The cutout, the balance bridge, and the balance wheel are the main landmarks on the upper portion of the top plate.
Most of the Seth Thomas models, with the exception of Model 5, have the balance bridge at the same level as the rest of the top plate and the balance wheel just below the back surface of the top plate. On Model 5, the only model with a full top plate, the balance bridge sits on top of the top plate with the balance wheel sandwiched between the balance bridge and the top plate.
The position of the balance bridge within the cutout of Seth Thomas pocket watch is the easiest way to tell quickly if the movement was designed with the open-face (pendant at 12:00 o’clock) orientation, or the hunting case (pendant at 3:00 o’clock) orientation. The balance bridges that point in the counterclockwise direction are open-face and those that point in the clockwise direction are hunting case. The only exception to this is the Model 4 key-wound movements, which are able to be cased in either orientation because they have no standard keyless winding bridge to be connected to the stem/pendant. The Model 4 balance bridge points in the clockwise direction.
Central and Lower (“Southern”) Landmarks
The remainder of the top plate may be decorated with one of the beautiful standard Seth Thomas engraving patterns or it may be a plain gilt surface. Stamped on the top plate of the movement you will usually find the serial number, the signature whether “Seth Thomas Thomaston, Conn.”, or a factory name grade, or a private label. Very few Seth Thomas top plates were intentionally left blank except for the engraving pattern. The top plate also contains multiple bearing and jewel penetrations corresponding to the simpler jewel and bearing penetrations found on the pillar plate hidden behind the dial. The top plate penetrations include the upper jewels or bearings for the:
pallet fork
escape wheel
fourth wheel (seconds)
third wheel
center wheel
Because Seth Thomas jewel placement practice varies. You cannot reliably determine jewel count from top-plate jewel settings alone. Learning to determine pillar-plate jewel counts is an important skill for collectors to determine the accurate total jewel count for a given movement.
Illustrations and Jewel Key
In the diagrams below:
Balance staff jewels (cap + hole) = red
Pallet fork hole jewel = blue
Escape wheel jewels = white
Fourth wheel (seconds) jewels = green
Third wheel jewels = yellow
Center wheel = orange
Model Identification Using Top Plate Configuration
Below, you will find the Ehrhardt American (EA) Numbered Drawings for each of the twenty-four Seth Thomas pocket watch models that Roy Ehrhardt identified. The Ehrhard American (EA) Numbered Drawings record the shape and penetration points of the movements’ top plates. The movements are described in great detail for us by Roy Ehrhardt in his “Identification and Price Guide to American Pocket Watches”. He devised this system using numbered diagrams, drawings of every American made pocket watch manufactured before 1999. This system covers every pocket watch produced by any manufacturer in the United States. The specific EA numbers for Seth Thomas movements range from EA 805 - EA 823. The only difference in nomenclature that you will see between what is used in Roy Ehrhardt’s EA Numbered Drawing system and what is used by the Seth Thomas Fan Space is in naming the 24th model, which was never named by the Seth Thomas Watch Company, “Pendant Model 24” instead of “Model 26”. I believe that Mr. Ehrhardt used the “Model 26” nomenclature because the Seth Thomas Watch Company alternately advertised their 6-size Centennial model as a 6-size movement, a 4-sized movement, and a compact 12-size movement, which would have required a 6-size Model 24, and 12-size Model 25, and a 4-size Model 26. In fact, the 12-size Model 25 was really a 12X6-size Model 24, and the 4-size Model 26 was really a 6-size Model 24 with a special snug dial, snug hands, and a snug case.
Seth Thomas Gilt Finish Movements
Seth Thomas manufactured gilt pocket watch movements in 18-size Model 1, Model 2, Model 3, Model 4, Model 5, Model 6, Model 10, Model 11, Model 12, and Model 13. Seth Thomas manufactured gilt pocket watch movements in 6-size Model 14.
Seth Thomas Nickel Movement Finishes
Seth Thomas manufactured nickel finish pocket watch movements in 18-size Model 2, Model 3, Model 5, Model 6, Model 7, Model 8, Model 9, Model 10, Model 11, Model 12, and Model 13. Seth Thomas manufactured nickel finish pocket watch movements in 6-size Model 14, Model 15, Model 16, Model 17, Model 18, and Model 19. Seth Thomas manufactured nickel finish pocket watch movements in 0-size Model 20. Seth Thomas manufactured nickel finish pocket watch movements in 16-size Model 21. Seth Thomas manufactured nickel finish pocket watch movements in 12-size Model 22, and Model 23. In short Seth Thomas manufactured nickel finish pocket watch movements in every model except Model 1 and Model 4.
Seth Thomas Two-Tone Movement Finishes
Seth Thomas manufactured two-tone finish pocket watch movements in 18-size Model 5, Model 6, Model 7, Model 8, Model 9, Model 12, and Model 13. Seth Thomas manufactured two-tone finish pocket watch movements in 6-size Model 15, Model 16, Model 17, Model 18, and Model 19.
Seth Thomas Gilt Damaskeened Movement Finishes
Seth Thomas manufactured gilt damaskeened pocket watch movements in 18-size Model 5, Model 8, Model 9, Model 12, and Model 13. Seth Thomas manufactured gilt damaskeened pocket watch movements in 6-size Model 18, and Model 19.
Movement Markings
Movement marking for the purposes of this of this subsection include the markings of movements that include the signature “Seth Thomas” on their top plate. The various styles of movement markings in each model tend to follow serial number ranges, though there is considerable overlap between different styles in certain model, and sometimes there are blocks of movement marking style that are dropped into the midst of another style because they represent a concentration of higher jewel count movements than that of the surrounding movements. Below you will be able to find diagrams adapted from the Ehrhard American Numbered Drawings of each presently known movement marking style in each model. For much more detailed information and photographs of the Seth Thomas movements bearing the many styles of markings please follow this link to the Movement Marking Styles page of this website.
You can support and assist our Seth Thomas Fan Space Research Project by uploading photographs of your Seth Thomas pocket watches to the Pocket Watch Database. Pocket Watch Database accounts are free of charge, and you will have full access to the photographs and descriptive information that you share, and you will have the ability to edit, change, or delete the information and photographs that you submit as you see fit.