This is a medium quality watch but well made. The old oil and grease found during disassembly indicates it has not been serviced in a while. Also there is quite a bit of wear on the upper center wheel pivot.
Pictures after watch has been cleaned. The mainspring did not need to be replaced, but the center wheel pivot has been repaired. The watch is clean, oiled and running well. There is some positional error (common in older watches like this one) It will gain around 1 min a day face up, and loose around 1 min a day stem up. So assuming, when it is used, it should even out the timing if it is in your pocket during the day and setting face up during the night. It will run 24 hours plus on a full wind.