First let me say I am not a Canon owner, so I am not an authority on this. I have a Vivitar 2X multiplier for 1970s time frame Canon lenses. It is a breach mount, cam thingie. I believe my brother had a Canon FTb? back then. It went to that. I looked at a Google search for FTb and it looks like what I remember, but it was in the 1970s and the statute of limitations has ran out on most of what I remember of may have done back then.

Untested and seems to be in good shape.

Would trade for 5 rolls of fresh Delta 100 in 120 or 136-36
Cash = How about $ 30.00 shipped CONUS and no returns.

Personal ck or money order with time to clear.
(Sorry, No PayPal, just turned those boys off for good after attack after attack on my finances.)