If you look at the rear edge, behind the speed ring, you will see four notches 90 degrees apart.
These are to hold the shutter while you disengage the cocking lever behind(inside the focus tube).
I have film in my camera right now, but you can look and see what holds it- just be careful of the
cocking and tripping mechanisms. I'll try to finish this roll this week.
Good luck, and hey! let's be careful in there!