Hmm, strange that the 12504 will fit on a newer 35 'cron but not the older, while the 12585 will fit on both.
I have both the 12585 and an IROOA, and neither can be reversed on the 35/2.8 Summaron (exactly the same dimensions as the v1 'cron, I believe) nor on the 50/2.8 Elmar in collapsed position.
I have a screw-in 12549 (designed for the modern Elmar-M) that fits very nicely, but that makes the lens not so compact in collapsed position.
I've been contemplating using a small round file to cut a notch in the rim of the 12585 to accommodate the focusing tab on the Elmar, but that might be sacriliege, no?
M9-P, Fuji X100