I have an old omega style development tank and the suction ring came out. I dont know where it fell out from. Does anyone know where this goes? Sorry for the dumb question.
If your talking that black rubber ring to the left edge of frame, it goes in the mouth of the tank. It slips inside and rests on a little ledge. It keeps the chemicals spilling out around the threads but to be honest, it's not very effective. I still make sure it's in place even though the tank still leaks. I have a few of them and use them for 135 film. The reel sucks for 12o. Freestyle photo sells professional reels that have a shelf in them and work great for 120. The reels do work inside the Omega.
As noted above, the ring goes in the top portion of the main body of the tank...it's a gasket. As JC notes, this ring sits on the ledge, near the top of the tank, inside the tank wall...