The Model 21*

1912 to 1915

The Model 21 was the company's only known 16-size movement, and it came well after most of the other American firms had launched their own 16-size designs. It was part of the Centennial Series, introduced around 1913 to mark their 100-year anniversary, and offered in three jewel counts on a single nickel pinstripe pattern. All three of the Centennial sizes within the grade were retailed in either nickel or 10/20-year gold-filled factory cases.

* This is an assigned model number

Grade Assignment

There are three known Model 21 grades. All of them are open-face with a simple pinstripe pattern on nickel plates.

* The 17-jewel Grade 336 is assigned.

The Centennial Grade

The Centennial Series was a named grade produced in three models, including the 16-size Model 21 family. While the standard Seth Thomas movements have three different jewel counts with the higher counts found only in the second smaller run, the Centennial grade had 7 jewels and have been reported only in the first serial number block.

Master Grade Chart

Production Dates and Totals

1912 to 1915

The first known appearance of the Centennial Series was in the 1913 Trade Price List, which would make sense given the company's established founding date of 1813. Since two distinct serial number blocks were in use it's likely that the actual debut was a little earlier, though a design date or granted patent number is not known. The three models of the Centennial Series were the only pocket watches to be listed in both the 1914 Catalog supplement and the addendum in the 1915 Catalog. The reasons behind the existence of a second block are unclear, since the first one could have continued all the way to SN 1700000. One explanation is that the M21 was made at different times and therefore blocked separately, but the only catalog known to advertise the Centennial Series was the 1913 edition, with no mention of any 16-size models in the 1909 volume.

62,000

Roughly 62,000 were produced in two widely separated blocks, with the first larger run starting at SN 1304501 up to 1360000, and a second smaller run beginning at SN 2593001 and ending at 2600000.

Master Block Chart

Seth Thomas Research

Seth Thomas Research

The Model 21*

1912 to 1915

Grade Lookup and Totals

Click on the charts below for more detailed information.

Grade Assignment

The Centennial Grade

Production Dates and Totals

1912 to 1915

62,000

The Tourist

Travel Watch

Period Ad Cuts

1913