Seth Thomas Mahogany Adamantine Mantel Clock

November 16, 2009 | By | 2 Replies More

“Adamantine” was Seth Thomas’ trademarked name for a celluloid finish over wood. Besides the mahogany color shown here, it was made in black, white, green, brown, tan and other colors. These cases are durable, and can usually be polished to look very nice. Sometimes the colors fade with age. Adamantine clocks were made from about the 1880s to the 1920s.

This beautiful mahogany Adamantine clock came into my shop recently with a broken time mainspring. Nothing too exciting about that, but I think this clock is so nice looking that I decided to show it here. I had previously repaired it 11 years ago, overhauling the movement and polishing the case and bezel.

I replaced the broken time mainspring with a Merritt’s P-1956 3/4 by .0165 by 96 inches (the original spring was 0.0172 inch thick). The pendulum takes a superb motion (almost too good) and so an even thinner mainspring would work. During my previous overhaul, I replaced the way too strong strike mainspring (an incorrect replacement) with a spring about 0.016 inch thick.

Repair job 4981.

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Category: American Clock Mainsprings, American Clock Repair, Seth Thomas Clock History

Last updated: June 5, 2010

Comments (2)

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  1. Bill Stoddard says:

    Most people have these repaired for their sentimental value, as the current market value is probably less that the price of an overhaul. If you like the clockm it would be worthwhile to hve it repaired so you can enjoy it.

    Details on my repair service are on the following web page:

  2. JEANNIE B says:

    I just acquired the mantel clock from my mother, (
    Seth Thomas #1091C ) I was wondering if it would be worth the expense to get it fixed and cleaned ?
    Thank You,

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