Compur button shutter

[gypsydog]

???

[Dan Fromm]

(1) Don't be so coy, share the listing so we can see whether you left out any information.

(2) Some Compur shutters have buttons on the side of the barrel. Sometimes it locks out the self-timer mechanism. Sometimes it sets the blade arrestor: cock the shutter, slide the button (forwards, IIRC), fire the shutter and it will stay open for focusing.