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I got it from the boyaetone link yesterday, good to hear to arrives quickly.
Knowing my luck it will turn out I need a Copal 3S retaining ring, just have to keep my fingers crossed on this one! I'll have to measure the thread on the lens itself which will be fraction more than the ring itself.It's very possible the shutter is actually a Copal 3S, which is M61x0.75. All the Fujinons I've seen in Copal 3 shutters, admittedly a small sample, were actually in Copal 3S - Copal weren't consistent about shutter markings and I've seen "3S" shutters marked only as "3". You're best off measuring the lens once you have it in hand.
Just measured the thread it is a 3S! Ordered from above now!