Okay here's a question for one of you vintage lens Gurus - Dan Fromm? Jim Galli? Anyone? - Can a 19" RDA be mounted directly into a Copal 3 shutter? What's the chance that Ilex #4 and Copal 3 front and rear diameter and threads are the same size? (I know I'm reaching here!)

I recently acquired from a successful Fleebay auction, a nice 19" Red Dot Artar mounted in an Ilex - Acme - Synchro - Whatnot - #4 shutter. After a good half hour putzing with it, I figured out how to work the shutter, being previously familiar with the workings of only the standard Copal (and one Seiko) shutters. So now that I have the Ilex #4 figured out, it sounds to be off by a fair bit in the 'mid speeds' (1/10, 1/25, 1/50) when compared with a known-good modern Copal shutter. I see that John Shiu has a nice black-ringed C-3 shutter for sale and I'm wondering just what the odds might be that I could just unscrew this puppy out of the Ilex and right into a Copal 3.

If not a direct fit, is it possible anyone could comment on the likelyhood of a minor SK Grimes retrofit of the RDA into a C-3? I'm sure ANYTHING is possible, but I'm not thinking of blazing new trails here, or going where no man has gone before on this. THanks for your advice.....