Quote Originally Posted by FrankB
... the flash mode switch araldited into the 'X' position (er, why?!?!?!?! Doesn't bother me, anyway.)
The "M" setting was for use with "M" synchronization Flash Bulbs - remember those? The flash contacts would close 50 milliseconds before the shutter would open to give the flash bulb enough time to reach an appropriate brightness.

If there was an anomaly in the design of the shutter (sounds like that was the case, from the posts here), it would have been a wise move to lock the shutter in place at "X" synchronization (no delay - for "electronic discharge" flash systems - LOTS faster than fash bulbs) to protect the shutter works.