Here is an example of a 1940s Seth Thomas mantel clock movement. This is the movement that replaced the No. 89 that was popular for many years. This one has the date stamp 42 6 on the rear lower left leg of the movement. Some of the other examples of this movement I’ve seen have another code stamped on the lower right movement leg as well, see my earlier posts: Plymouth (by Seth Thomas 1940s mantel clock, 1940s 8-day Seth Thomas Time and Strike Clock Movement, Two Seth Thomas “Plymouth” Mantel Clocks, 1938 and 1945.
This type of movement runs very efficiently, and can use thinner mainsprings (if they need replacing). My earlier post, Plymouth (by Seth Thomas 1940s mantel clock, describes the mainsprings this movement needs.
Repair job 5815. Polish pivots, install 12 bushings.