I ordered a retaining ring for a Copal #3 shutter for a lens that won't be here for 2-4 weeks. I tried it on a 250mm Fujinon SF that's mounted in a Copal shutter not marked #3 or #3s. The ring is a bit too large. This would make sense if the Fujinon is mounted in a 3s shutter but, AFAIK, the Fujinon was never mounted in a 3s shutter. Am I wrong? Currently, I don't know if I should contact the seller.