[Leica] M3 Take up spool

[lew at speakeasy.net (Lew Schwartz)]

I just acquired an M3 and I have some questions about the takeup spool.
1. Since it seems easy to lose, is there a hopefully inexpensive source for
replacements?
2. The metal sheath that surrounds the spool has what looks like a spring
clip on its upper end, but since the film is inserted into the spool rather
than under the clip, the clip seems to have no purpose. What's it for?
3. I notice that another M's take up spool is knurled on the bottom, I guess
to facilitate removal. Mine's smooth. What's the significance of the
difference.
4. I also notice that the instructional graphic showing how to load film is
different from one M3 to another. What's the significance of this?
5. While my film counter seems to reset properly, it moves to frame 1 before
I get to wind off some blank frames to get to the unexposed film. Comments,
please.
-Lew