The Model 20 was the company's only known 0-size movement, measuring just a little over an inch in diameter. It was a bold move for Seth Thomas, with the popularity of wristwatches on the rise but peaking well after WWI. They first arrived in the 1908 catalog, offered in three jewel choices in only a stem-set hunting configuration as an uncased movement or as a wristwatch with a factory-supplied leather strap.
* This is an assigned model number. The factory designation is not known.
There were only three known grades; all nickel-plated and hunting but with different jewel counts.
The 0-size Grades 1, 3, and 9 first appeared in the 1908 catalog and continued in all of the known catalogs until the end of production in 1913, with prices of all the grades doubling by the end of their run. All Model 20s were made in hunting configuration with a choice of a standard hunting dial to be used for wristwatches or with a conversion dial for open-face.
The Model 20 was made in a single run of some 5,000 movements with all examples between SN 2,000,001 and 2,004,800.
The watches logged in the M20 chart are all reported examples or verified from photos.
If your watch isn't on this SN chart please send us a picture.
The Model 20 was offered as a wristwatch with a choice of straps or an uncased open-face watch, because none of the period company adverts actually listed a 0-size nickel or gold-filled pocket watch case. The factory wristwatch case was nickel, with a black Morocco or pig skin strap, selling for $14 in 1908.
An unfinished gilt 7-jewel Model 20 has been reported, but with no markings whatsoever. No finished gilt variants have been logged, raising questions about whether this could have been a prototype.
There is no mention of a gilt Model 20 in any of the known catalogs.