Seth Thomas 6-size Century Model 18 is represented in the Ehrhardt American Numbered Drawings as EA 821 and can be identified through the use of the drawing below:

Mechanism & Dial View

Pillar Plate View

Model 18 was chosen by Seth Thomas to represent their powerhouse Factory Name Grade “Century” in the 6-size portion of production. Many of the 18-size private labels are represented in this 6-size incarnation of the Century Series including: Athabasca, Century U.S.A., Knickerbocker Watch Co., Republic U.S.A., Sentinel U.S.A., and Stratford U.S.A. Other Model 18 private labels that were not present in the 18-size Century Series include: Adonis U.S.A., Countess Janet, Lake Shore, and Waldorf U.S.A., many of which were the hunting version to partner with a 6-size Model 24 open-face version.

Click this link to open the Model 18 Photo Album in a new tab.

As a study of Model 17 teaches us, when Seth Thomas designed a 6-size movement to utilize the Breguet hairspring a subtle modification was made to the regulator and the balance bridge to maximize the effectiveness of the Breguet hairspring for that movement. That subtle design modification was also found on Model 19 regulators and balance bridges.

The Seth Thomas 6-size Model 15 and Model 16 utilized a flat hairspring. When Seth Thomas decided that Model 17 would utilize the Breguet hairspring the regulator and balance bridge were modified to maximize the efficiency of the new hairspring. In the images below you can compare Model 16 and Model 17 to see the modifications made to accommodate the new technology.

Seth Thomas decided to once again utilize the flat hairspring in their 6-size Century Grade Model 18 movements; but decided to use the Breguet hairspring with the modifications to the regulator and balance bridge in their Model 19 movements.

In the 6-size movement that utilize a flat hairspring the balance bridge extends beneath the entire circumference of the regulator ring. In the 6-size movements that utilize a Breguet hairspring a portion of the balance bridge is cut or milled away to permit a shorter regulator arm to grasp the Breguet hairspring closer to its center. This modification to the balance bridge is difficult to see with the regulator in place; but it can be detected by swinging the regulator pointer clockwise to see if it will extend beyond the edge of the balance bridge. With a flat hairspring the pointer easily extends beyond the balance bridge as long as the hairspring stud is installed properly and not extending above the surface of the bridge. A regulator designed for the Breguet hairspring will only extend until the regulator arm hits the continuation of the balance bridge below the regulator ring. This will prevent the regulator pointer from extending beyond the edge of the regulator. This limitation of the regulator swing becomes a simple test to tell the Model 18’s from the Model 19’s. The production of Model 18 movements subsequent to serial number 4,000,000 also utilized the Breguet hairspring with the same modifications to the regulator and balance bridge.

In the images below can compare the sizes of the regulators designed for use with the Breguet hairspring, Model 17 and Model 19, with the regulators designed for use with the flat hairsprings, Model 16 and Model 18.

The image on the left shows the Model 17 regulator on the left with a shorter regulator arm to engage the Breguet hairspring closer to its core. The regulator on the right is from the older Model 16 designed for use with the flat hairspring.

The image on the left shows the Model 19 regulator on the left with a shorter regulator arm to engage the Breguet hairspring closer to its core. The regulator on the right is from the older Model 18 designed for use with the flat hairspring.

Seth Thomas Model 18 Movement Markings

There was no style of standard, non-private label, movement markings used on Seth Thomas Model 18 pocket watches. All Seth Thomas Model 18 pocket watches were manufactured as private label pocket watches. Private Label pocket watches in the Model 18 Photo Album include: Adonis U.S.A.; Athabasca; Century U.S.A.; Countess Janet; Knickerbocker Watch Co.; Lake Shore; Republic U.S.A.; Sentinel U.S.A.; Stratford U.S.A. and Waldorf U.S.A.

None of the movements in Model 18 were signed Seth Thomas, Thomaston, Conn.

Model 18 images can be seen starting on Page 1 of the Seth Thomas Model 18 Image Gallery of the Pocket Watch Database.

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.

All Watches in Model 18 are Private Label Pocket Watches and Hold the Factory Named Grade “Century”

EA 821 – Adonis U.S.A. – 6-size – Model 18 – Serial# 992077 – 7 Jewels - Factory Named Grade Century

EA 821 – Adonis U.S.A. – 6-size – Model 18 – Serial# 4013768 – 7 Jewels - Factory Named Grade Century

Adonis U.S.A. is a private label in Seth Thomas 6-size hunting Model 18 and Seth Thomas 6-size open-face Model 24.

Adonis U.S.A.

EA 821 – Adonis U.S.A. – 6-size – Model 18 – Serial# 991674 – 7 Jewels - Factory Named Grade Century

EA 821 – Athabasca Made in U.S.A. – 6-size – Model 18 – Serial# 3252188 – 7 Jewels - Factory Named Grade Century

EA 821 – Athabasca Made in U.S.A. – 6-size – Model 18 – Serial# 3252273 – 7 Jewels - Factory Named Grade Century

Athabasca is a private label in Seth Thomas 18-size open-face Model 12, and 6-size hunting Model 18.

Athabasca

EA 821 – Century U.S.A. – 6-size – Model 18 – Serial# 983024 – 7 Jewels - Factory Named Grade Century

Century U.S.A. is a private label in Seth Thomas 18-size Model 10, Model 11, Model 12, and Model 13, and 6-size hunting Model 18 and 6-size open-face Model 24. Access the Seth Thomas Photo Album by Model Number to see more Century U.S.A. pocket watches.

Century (Factory Named Grade) - Century U.S.A. Private Label

EA 821 – Countess Janet – 6-size – Model 18 – Serial# 966625 – 7 Jewels - Factory Named Grade Century

Countess Janet is a private label in Seth Thomas 6-size hunting Model 18 manufactured for Sears, Roebuck & Company for sale in their mail order catalog.

Countess Janet

EA 821 – Countess Janet – 6-size – Model 18 – Serial# 962426 – 7 Jewels - Factory Named Grade Century

EA 821 – Knickerbocker Watch Co. – 6-size – Model 18 – Serial Number 4000513 – 7 Jewels - Factory Named Grade Century

Knickerbocker Watch Co. is a private label in Seth Thomas 18-size open-face Model 12 and Seth Thomas 18-size hunting Model 13, Seth Thomas 6-size hunting Model 18 and Seth Thomas 6-size open-face Model 24.

Knickerbocker Watch Co. New York

EA 821 – Lake Shore – 6-size – Model 18 – Serial Number 998852 – 15 Jewels - Factory Named Grade Century

The private label pocket watch, Lake Shore, was manufactured for sale in the Montgomery Ward Co. mail order catalog.

Lake Shore is a private label in Seth Thomas 18-size open-face Model 5 with 17 jewels at grade 182, 6-size hunting Model 18 with 15 jewels at grade 205, and 12X6-size open-face Model 24 with 15 jewels at grade 322. The signature on the dial of the Model 5 Lake Shore is spelled out as one word, “Lakeshore”. The signatures on the dials of the Model 18 Lake Shore and the Model 24 Lake Shore, as well as the signatures engraved on the movements of all three models are all presented as two words, “Lake Shore”. The Montgomery Ward Co. catalog also advertised using the two-word name “Lake Shore” for this private label. The 12X6-size version was advertised (see image below) as a Compact 12-size Lake Shore.

Lake Shore should not be confused with the private labels “Lakeside”, also manufactured by Seth Thomas in Model 8 and Model 9 for sale in the Montgomery Ward Co. mail order catalog; or the private label “Lakesite” manufactured by Seth Thomas in Model 8 and Model 9 for sale in the J. M. Smyth Co. mail order catalog.

Lake Shore

EA 821 – Republic U.S.A. – 6-size – Model 18 – Serial Number 969996 – 7 Jewels - Factory Named Grade Century

EA 821 – Republic U.S.A. – 6-size – Model 18 – Serial Number 987920 – 7 Jewels - Factory Named Grade Century

EA 821 – Republic U.S.A. – 6-size – Model 18 – Serial Number 4003260 – 7 Jewels - Factory Named Grade Century

Republic U.S.A. is a private label in Seth Thomas 18-size Model 12 and Model 13, and 6-size Model 18, Model 19, and Model 24. The Pocket Watch Data reports that Seth Thomas was one of the manufactures making Republic U.S.A. movements for the Illinois Watch Case Company.

Republic U.S.A.

EA 821 – Republic U.S.A. – 6-size – Model 18 – Serial Number 969761 – 7 Jewels - Factory Named Grade Century

EA 822 – Sentinel U.S.A. – 6-size – Model 18 – Serial Number 3256317 – 7 Jewels - Factory Named Grade Century

Sentinel U.S.A. is a private label in Seth Thomas 18-size Model 12 and Model 13. and 6-size Model 18.

Sentinel U.S.A.

EA 821 – Stratford U.S.A. – 6-size – Model 18 – Serial Number 980589 – 7 Jewels - Factory Named Grade Century

Stratford U.S.A. is a private label in Seth Thomas Model 12, and Model 18, manufactured for John M. Smyth Company by the Seth Thomas Watch Company for their catalog.

Stratford U.S.A.

EA 821 – Waldorf U.S.A. – 6-size – Model 18 – Serial Number 4010508 – 15 Jewels - Factory Named Grade Century

EA 821 – Waldorf U.S.A. – 6-size – Model 18 – Serial Number 4010986 – 15 Jewels - Factory Named Grade Century

Waldorf U.S.A. is a private label in Seth Thomas 6-size hunting Model 18 and Seth Thomas 6-size open-face Model 24 manufactured for Sears, Roebuck & Company for sale in their catalog.