I recently acquired such a shutter. I think it may have been intended for use with a Schneider 135/270mm convertible lens. One scale starts at f5.6 and goes to f45. The second scale starts at f12. I intend to use it with a 135mm lens presently mounted in a Copal #0. The Synchro shutter has an M setting for flash bulbs. I use bulbs on occasion just for fun. My Copal had only an X setting for electronic flash. I recently use flash bulbs with my Crown Graphic at my son's wedding. Got a lot of comments and questions. Lots of fun but several of my shots were failures because I used 1/30 shutter speed to capture the delayed flash. My question is whether the f-stop scale on my Synchro will match up to any 135mm lens or will I have to take test shots to determine any compensation that might be required. My lens is a f5.6 Rodenstock Sironar N that I acquired from Kerry Thalmann.