Balance Bridge Engraving Patterns
Seth Thomas pocket watch balance bridges contribute and support critical components that enable the superb accuracy of Seth Thomas pocket watches. In addition to this essential role in the mechanical function of the watch movements, the balance bridges present with beautiful decorative engraving patterns unique to each pocket watch model, enhancing the appealing combination of elegance and practicality that compliments the high degree of craftsmanship and engineering genius that went into the production of Seth Thomas pocket watch movements.
If this introductory statement sounds like the gateway to an art appreciation lesson; fear not. As a collector, or a watchmaker it is important to be able to utilize the clues embedded within the components of your watches to discern whether or not they are original components, and to assist in clarifying the identity of the mechanism that you are observing. The decorative engraving patterns on the balance bridges of Seth Thomas pocket watches will talk to you if you are alert enough to listen.
In this article you will be provided with a comprehensive visual reference guide to the engraving patterns on the balance bridges of all twenty-four Seth Thomas pocket watch models.
Take a moment to consider the features of, and positions of, the components of the two Seth Thomas pocket watch movements pictured below. What are they telling you that would provide documentary evidence of the watches’ identities?
Unknown Pocket Watch Movement Number 1
Unknown Pocket Watch Movement Number 2
A simple and obvious component position in this example is the positioning of the balance bridges. They are both projecting from the circumference of the movement and pointing in the counter-clockwise direction. This strongly suggests that they are both open-face pocket watches. The Seth Thomas open-face pocket watch models are the 18-size Model 1, 18-size Model 3, 18-size Model 5, 18-size Model 6, 18-size Model 8, 18-size Model 10, 18-size Model 12, 16-size Pendant Set Model 21, 12-size Pendant Set Model 22, 12-size Bridge Model 23, and 6-size Pendant Set Model 24. 18-size Model 4 is convertible to either open-face or hunting case orientation because it is key wound and key set; having no winding stem to dictate either orientation.
That narrows the field of possibilities from 24 Seth Thomas models to only 11 possible models.
Next we should look at the shape and penetration points of the top plate. They are described in great detail for us by Roy Ehrhardt in his “Identification and Price Guide to American Pocket Watches”. He devised a system using numbered diagrams, drawings of every American made pocket watch manufactured before 1999. The EA (Ehrhardt American) numbers for Seth Thomas movements range from EA 805 - EA 823.
The best matches with the EA Numbered Drawings for Unknown Pocket Watch Movement Number 1 are EA 813 and EA 813B.
EA 813
EA 813B
Key differential markers in making a correct match include: EA 813 has the same squared plate cut near the balance wheel as Unknown #1, EA 813B has a deeper rounded cut pattern near the balance wheel; EA 813 has the same casing screw positions as Unknown #1 at approximately 180 degrees from each other, the casing screws on EA 813B are approximately 100 degrees from each other; EA 813 has the same sharp tip on the wing of the balance bridge as Unknown #1, EA 813B has a blunted wing tip; EA 813 has the same tab for the plate screw near the base of the balance bridge as Unknown #1, EA 813B has a fuller curve to the plate with no need for a screw tab; the engraving and dimensions of the balance bridge on EA 813 are a match with Unknown #1, while the engraving on the balance bridge of EA 813 does not match that of Unknown #1 and the bridge on EA 813A appears to be smaller.
The New Century Models, 12 and 13, had some differences from the Old Century Models as described in the 1904 Seth Thomas Watch Material Catalog, “These movements are thinner and have smaller balance bridges than old models 10 and 11”.
Visual evidence seems to support an initial identification of Unknown #1 as a Seth Thomas Model 10 “Colonial U.S.A.” movement.
The best matches with EA Numbered Drawings for Unknown Pocket Watch Movement Number 2 are EA 813A and EA 813C.
EA 813C
EA 813A
The key differential marker in making a correct identification of Unknown #2 rests entirely in the dimensions and shape of the balance bridge. The spiral vine balance bridge engraving pattern at the base of Unknown #2 is not a match with the blank pattern on the base of the EA 813A drawing and is not a match for the geometric engraving pattern on base of the EA 813C drawing. The size of the balance bridge on Unknown #2 is narrower than that of Unknown #1 and of EA 813A. Its size appears to be a match with EA 813C.
Visual evidence seems to support an initial identification of Unknown #2 as a Seth Thomas Model 12 “Colonial U.S.A.” movement.
Upon measuring and comparing the outside diameter of the regulator ring on the balance bridges of the “Unknown #2” Model 12 Colonial and an available Model 10 Pan-American; the Model 12 Colonial’s regulator ring measured 5.64mm, and the Model 10 Pan-American’s regulator ring measured 6.86mm. The engraving inside the larger Model 10 regulator ring is a lotus blossom. The space inside the smaller Model 12 regulator ring is only large enough for the engraving of a daisy blossom. The photographs below document those measurements and show a side-by-side comparison of a Model 12 balance bridge with the more standard engraving pattern next to a visibly larger Model 10 balance bridge.
The spiral vine pattern is seen on the base of the balance bridge of Model 10 movements and some of the early movements of Model 12, prior to 1904 and prior the Model 12 movements being stamped with a serial number.
Other visual clues that would go into making an initial identification include the movement markings. In this instance you can see through the photographs of a Seth Thomas 18-size Model 10 Private Label Colonial U.S.A. photographed at the American Clock & Watch Museum in Bristol Connecticut in April 2024, that the Model 10 movement markings include “U.S.A.” below “Colonial”. The Model 12 movement markings do not. I do not know of any other source that has published this differential fact; but I can only hope that seeing is believing.
The importance of making historical background information freely available to all who have interest in the roots of the American clock and watch industry cannot be overstated. Information that is not freely shared not only confounds the research and practice of present day horologists; but will likely be forever lost to the future generations of horologists.
The Pocket Watch Database, founded and administered by Nathan Moore, by serving as a collective repository for the studies and research of many, is playing the greatest role in collecting, organizing, consolidating, and freely disseminating invaluable information to the horological community and the public at large.
Another visual clue that would go into making an initial identification includes the lack of serial numbers on these movements. None of the Seth Thomas Model 10 movements had serial numbers stamped into the top plate; although partial serial numbers can be found on the pillar plate under the dial, as well as on certain components such as the balance bridge. Some of the earlier Model 12 movements also lack a serial number on the top plate. In the 1904 Seth Thomas Watch Material Catalog it was stated, regarding Model 12 and Model 13 that; “These movements are not numbered”. This is how we know that the numbered Model 12 and Model 13 movements were produced in the years sometime after 1904. Almost all other Seth Thomas movements in all of the other Seth Thomas models have a serial number stamped clearly on the top plate.
A confounding factor in making this quick visual identification is the Model 12 Colonial U.S.A. having an engraving pattern on its balance bridge that is different from the vast majority of other Model 12 movements; but very similar to the Model 10 and 11, Old Century, models’ engraving pattern. This rare Model 12 engraving pattern is not actually the same as the Model 10 pattern. The direction of the spiral pattern is opposite. It is also the case that this rare Model 12 engraving pattern is not completely unique to the Colonial USA private label in Model 12. I have an example of a Model 12 Century USA private label with the same rare engraving pattern on its balance bridge.
Seth Thomas Balance Bridge Engraving Patterns by Model Number
Some considerable brainstorming must have occurred when planning out the combination of consistency and diversity of the Seth Thomas balance bridge engraving patterns. Each 18-size, 16-size, 12-size, and open-face 6-size Seth Thomas model has a unique set of engraving patterns used on its balance bridges. The 6-size hunting Model 14, Model 15, Model 16, Model 17, Model 18, and Model 19 share one consistent engraving pattern. 6-size Model 18 has an additional decorative engraving pattern. In addition to these unique decorative balance bridge engraving patterns many of the balance bridges also exhibit the same overall finish pattern as the rest of the top plate. The 12-size Bridge Model 23 only used a unique decorative bridge engraving pattern on the early serial numbers. After that the balance bridges only exhibit the overall finish of the rest of their top plate. These are the only Seth Thomas balance bridges without a decorative engraving pattern.
When assessing and comparing the balance bridge engraving patterns it is useful to observe them in three component areas:
1. The engraving around the balance bridge screw.
2. The engraving between the regulator scale and the regulator ring.
3. The engraving inside the regulator ring.
- An additional significant point of comparison is whether the tip of the bridge’s wing comes to a sharp point or is blunted.
18-size Seth Thomas open-face Model 1 has three varied decorative balance bridge engraving patterns.
A spiral vine pattern with no engraving inside regulator ring; sharp pointed wing tip
A spiral vine pattern with engraving inside regulator ring; sharp pointed wing tip
A spiral vine pattern with heavy engraving inside regulator ring; sharp pointed wing tip
18-size Seth Thomas hunting Model 2 has two distinct decorative balance bridge engraving patterns.
A spiral vine pattern; blunted wing tip
A trident-like pattern; blunted wing tip
A trident-like pattern; blunted wing tip
18-size Seth Thomas open-face Model 3 has two distinct decorative balance bridge engraving patterns.
A spiral vine pattern; sharp pointed wing tip
A geometric pattern; sharp pointed wing tip
A geometric pattern; sharp pointed wing tip
18-size Seth Thomas convertible Model 4 has one distinct decorative balance bridge engraving pattern.
A geometric pattern; sharp pointed wing tip
18-size Seth Thomas open-face Model 5 has three distinct decorative balance bridge engraving pattern.
Vines with blossoms and seeds in 2nd component area; sharp pointed wing tip
Vines with blossoms but no seeds in 2nd component area; sharp pointed wing tip
Vines without blossoms or seeds in 2nd component area; sharp pointed wing tip
18-size Seth Thomas open-face Model 6 has three distinct decorative balance bridge engraving patterns.
A geometric pattern without engraving inside the regulator ring; sharp pointed wing tip
A geometric pattern with Lotus Blossom engraving inside the regulator ring; sharp pointed wing tip
A spiral vine pattern with Lotus Blossom engraving inside the regulator ring; sharp pointed wing tip
18-size Seth Thomas open-face Model 7 has three distinct decorative balance bridge engraving patterns.
A geometric pattern; sharp pointed wing tip
A spiral vine pattern without engraving inside the regulator ring; sharp pointed wing tip
A spiral vine pattern with engraving inside the regulator ring; sharp pointed wing tip
18-size Seth Thomas open-face Model 8 has two distinct decorative balance bridge engraving patterns.
Movements from the Eagle Series - New Model, Model 8 and Model 9 “are thinner and have smaller balance bridges than previous models” in the Eagle Series - Old Model, Model 6 and Model 7.
A butterfly pattern
A geometric pattern
18-size Seth Thomas open-face Model 9 has two distinct decorative balance bridge engraving patterns.
Movements from the Eagle Series - New Model, Model 8 and Model 9 “are thinner and have smaller balance bridges than previous models” in the Eagle Series - Old Model, Model 6 and Model 7.
A geometric pattern
A butterfly pattern
18-size Seth Thomas open-face Model 10 has one distinct decorative balance bridge engraving pattern.
A spiral vine pattern, and a butterfly pattern, with Lotus Blossom; sharp pointed wing tip.
18-size Seth Thomas open-face Model 11 has one distinct decorative balance bridge engraving pattern.
A spiral vine pattern, and a butterfly pattern, with Lotus Blossom; sharp pointed wing tip.
18-size Seth Thomas open-face Model 12 has two distinct decorative balance bridge engraving patterns.
A spiral vine pattern
A geometric pattern
18-size Seth Thomas hunting Model 13 has one distinct decorative balance bridge engraving pattern.
A geometric pattern
6-size Seth Thomas hunting Model 14 has one distinct decorative balance bridge engraving pattern.
A spiral vine pattern
6-size Seth Thomas hunting Model 15 has one distinct decorative balance bridge engraving pattern
A spiral vine pattern
6-size Seth Thomas hunting Model 16 has one distinct decorative balance bridge engraving pattern
A spiral vine pattern
6-size Seth Thomas hunting Model 17 has one distinct decorative balance bridge engraving pattern
A spiral vine pattern
6-size Seth Thomas hunting Model 18 has two distinct decorative balance bridge engraving patterns.
A spiral vine pattern
A bass clef pattern
6-size Seth Thomas hunting Model 19 has one distinct decorative balance bridge engraving pattern.
A spiral vine pattern; sharp pointed wing tip.
0-size Seth Thomas hunting Model 20 has one distinct decorative balance bridge engraving pattern.
A vine pattern.
16-size Seth Thomas open-face Model 21 has one distinct decorative balance bridge engraving pattern.
A geometric pattern.
12-size Seth Thomas open-face Model 22 has one distinct decorative balance bridge engraving pattern.
A spiral vine pattern.
12-size Seth Thomas open-face Model 23 has three distinct decorative balance bridge engraving patterns.
Overall plate pattern with a decorative geometric balance bridge pattern - only found on earliest production.
Overall plate pattern - no decorative balance bridge pattern.
Overall plate pattern - no decorative balance bridge pattern.
6-size Seth Thomas open-face Model 24 has one distinct decorative balance bridge engraving pattern.
A geometric pattern.
Cupid’s Bow and Arrow; sharp pointed wing tip.