Bronica sq back question

My brother in law is a professional photographer and for christmas he gave me his old bronica outfit he used before he went digital. It included 2 bodies, 4 lenses and a small pile of backs and accessories.

Most of the backs are 220. But I noticed one was missing the badge denoting that it is a 220 or 120 back. There was an exposed roll of film rattling around in the box of stuff so I ran that through and found it to be a 120 back, sweet! I then proceeded to use that roll to practice loading my developing reels and then tossed it.

I noticed there is another back missing its badge but I have no throwaway film to run through it. Is there any way to tell if it is 120 or 220 just by looking at it? Or maybe a way to trick the camera into thinking there is film so I can see how high the counter goes up? Thanks!

I don't think it's possible to tell the difference by looking at the backs or inserts. If it's convenient, you should first ask your brother-in-law. If it's not, then buy a roll of 120 film and see if it winds through it. If it has normal tension, then it's for 120. If it feels tight, don't force it. It will be for 220. Go to a dark area (darkroom, changing bag, etc.) and take it out and wind the film back onto the spool and save it for use in the other back.

Dave

When I use 120 film in the 220 back I have, I have to fire off a few extra frames after the 120 roll is done just to be able to fully rewind.

That'd be one way of telling.

Look at the exposure counter. On one of my 220 backs, I can just see the "24" hiding at the edge of the window. Also, if the "S" and the "1" are right next to each other, that would indicate that there are lots of frame numbers to crowd onto the counting reel. If there's a space roughly equal to the height of the numbers, you might be looking at a 12 exposure display.

It looks like it is another 120 back, thanks guys!