I've somehow got hold of three of these things, of which two are fine and one is for parts. The "parts" one has no other problem than that the speed changing system is rusted stuck. Completely stuck. It works fine, but only at 1/30.

They also have interchangable front panels (two of them do), and I've got an extra front panel. So that's three different lens threads on the good "threadmount" one. The last one has a "baffle", meant for front mounting on a lens of suitable diameter. Just push it on, and it will keep in place for long enough to take a picture.

I don't know if this goes for all TP shutters, but the front panel on mine just lifts off to give access to the workings.