Late Seth Thomas Adamantine Mantel Clock, 1918

This Seth Thomas Adamantine mantel clock is dated June 1918 on the bottom of the case (date code 81F, where F represents the month, and 81 are the last two digits of the year reversed). I’ve seen many examples on earlier clocks where the date code has all 4 digits of the year, but this is the first time I’ve seen just 2 digits.

This later example of the Adamantine case has a simplified design with no pillars or Lion’s heads, and the dial is painted metal. See Seth Thomas Adele Adamantine Mantel Clock for an example of the earlier case design.

Case height 10 inches, width 12.5 inches, minute hand length 2 9/32 inches. The pendulum bob is lead with a brass cover on one side, weighs 5.4 ounces and is 45 mm in diameter.

The original mainsprings have the following measurements:

Time: 3/4 inch wide by 0.0175 inch thick

Strike: 3/4 inch wide by 0.0171 inch thick.

See more photos.

Job 5577. I did limited repair on the movement: cleaning, polished the worst pivots, installed 8 bushings (correcting 3 that were previously installed off-center), and tightened the strike click rivet.

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  1. Good Morning,

    The clock pictured above is just like the one i just purchased. It does not have a key. I have to pick it up today from where i purchased it and do not have any idea how to pack it except for taking the pendulum out. Can you help as to where i can find a key for this clock and packing it. It is the same as above, A Seth Thomas Adamantine clock that is in a simple case with no pillars. Just as above.


  2. Hi. I just recently inherited a clock like the one pictured here (job number 5577). I can’t seem to find a date on mine though. It hasn’t been running for quite some time so I decided to wind it and see how it works tonight, but the pendulum stops swinging after a short time…do you know why this might be? Also, do you know much a clock like this is valued at…ballpark? Any information you can give me would be helpful because right now I only know it’s a Seth Thomas clock, which is a category that I know nothing about. Thanks!

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