Probably a silly question!

[ozonepirate]

I have an MPP with a schneider 150 lens, now next to the little switch that opens the lens is a small button........What does it do???

[J Ney]

one silly question deserves another.... what's a "MPP?" Never seen that acronym before.

[Don Dudenbostel]

What kind of shutter? How about a picture? There have been dozens of shutter types made over the decades. My wild guess is a compur 0 and the button locks the cocking lever open. My 135 Xenar in a Compur 0 has a little button next to the cocking lever Thad is depressed when you fire the shutter and it blocks the cocking lever from traveling it's full throw and opens the shutter so you can focus.

[Andrew]

I have an older 150mm symmar convertible in an compur shutter... that one has a small button where you describe which is for the self-timer. IF it's the same as mine you push the button back as you cock the shutter and then when you release the shutter the clockwork mechanism retards the firing for a few seconds

[rdenney]

one silly question deserves another.... what's a "MPP?" Never seen that acronym before.

Micro Precision Products, a former British maker of pretty good technical and press cameras.

Rick "not relevant to the question, however" Denney