This hairspring looks like it has problems, but turned out to just be dirty. At first it seems like the coils were out of shape and touching each other.
But with the old oily dirt removed, it shaped right up.
Here's the mainspring, cleaned and installed in the barrel.
This watch stayed on the bench for awhile. I found a replacement stem, but the real problem turned out to be that there is not smooth action in and out of the stem. There is too much play in it, and it tends to pull to one side or another. Also, if not pulled perfectly straight out it was possible to pulled the stem right out of the movement.
There's a little part called a detent that acts as a lever when the stem is pulled. One part of this part "snaps" against a spring so as to stay out when pulled. It is actuated by a pin at one end that sits in front of a shoulder on the stem. When the stem pulls out it pushes the pin and moves everything to setting mode. This pin also hold the stem in.
But on this watch the plates themselves are so worn that the stem can move around too much and get out from behind the pin, and thus come all the way out of the watch.
To attempt to fix this, at least as much as possible for an antique, I first made the detent thinner by removing metal from the underside. This way when it is installed it sits lower down, and the pin end then protrudes deeper against the stem.
Secondly, I filed away a minuscule portion of the lever end so that slightly less pull is needed to snap it into setting mode.
I don't yet know if this will work. If it doesn't, I'm not sure there's any other possibilities. When the body of the movement is worn and distorted, there's few options.
This is a 20/0 size watch; almost as small as they get. I should note that one of these photos above shows two of these parts. One in in place in the movement and the other loose. I tried replacing the detent first, but no luck there fixing the trouble.
Interestingly, instead of dial foot screws, this watch has two screws, at the top and bottom respectively, holding the dial on.
The movement runs quite well. But the stem remains an issue.











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