Revisiting this thread after conducting speed tests and attempting to correct, I've reached a dead end for now. There is no real way provided on this shutter for meaningful timing adjustments. This leads me to ask a question of perhaps some clock people (of which I am not one). Specifically my biggest question is: over 90 years time, how much spring strength typically gets lost? There are not really many springs in this simple Betax shutter, but I am just about convinced it will never be possible to make the adjustments needed without my fabricating new springs. Would you agree? Here is what I have now: 1/2 ok, 1/5 ok, 1/10=11.5, 1/25=1/33, 1/50 does not exist. Nothing past 1/33. And believe me, I've done a lot of spring bending to get this compromise. The simplistic clockwork-and-escapement mechanism only has one spring and I highly suspect it has no strength remaining to hold against the big hairpin spring that drives the whole shutter.