I just repaired this Seth Thomas mantel clock in a mahogany color Adamantine case. It has a No. 89 movement with a solid back plate. The case is 16 1/4 inches wide (including feet) and 11 inches tall. The bottom of the case has date code 81B (February 1918).
The escape wheel had two teeth that were too short due to damage by a previous repairer. The slide show below shows that the damaged teeth were removed, a brass plug inserted, and then 2 teeth filed to shape.
Both mainsprings were original Seth Thomas springs, one .0177 inch thick and the other .0165 inch thick. I don’t know for sure which one was originally on which side (time or strike). The .0177 inch thick spring was too strong. The thinner spring did not unwind smoothly. I replaced both with Merritt’s P-1956 springs 3/4 inch wide x 0.0165 inch thick x 96 inches long.
One thing strange about the case is that one end is mahogany Adamantine, but the other end is black! (see slide show below). It appears to have been made this way.
Repair job 4830
Share this post: