I have a 1870's Seth Thomas that is time and Strike (hour only). After I wind the strike side, it has a tendency to add a hour (clock shows 7 and it chimes 8 or 9) or two. It doesn't always do it, but lately it has been doing more. I've made sure the time change wire(the small wire that hangs down that you push up to change the hour) is not hanging up. Any ideas?

I see this is an old post, but it does not appear to have been answered, so I'll give it a shot.

I have had this happen on some early 1900's Seth Thomas two train movements, when I accidentally assembled them with the strike locking wheel off by a tooth or two. Winding temporarily takes the pressure off the train, and because the lock wire is not centered in the detent, it lifts, throwing the strike off by one notch on the count wheel. I have also seen this same problem when someone assembled the strike improperly, and effected a temporary "fix" by bending the count wheel wire, so that the crutch falls into a slot, instead of hitting along one side or the other of a notch.

OOPS! Forgot to take into account the statement that it seems to be getting worse lately. That can happen if the strike lock was just barely engaging, and one of the strike pivot bushings (usually the third wheel in the train) has worn to the extent that the lock wheel is now moving just a tad further than it should when winding alternately removes and applies power to the train.