Hey, that was quick! Customs got the lens through in record time and I have it in hand. Its condition is quite clean for an old brass lens, the aperture wheel works, and at a quick look the glass appears good. So I'm entirely happy with my experimental order.
The mounting threads are 44mm, as near as I can tell, which seems like a plausible "tape-to-fit" job for the Ilex #3 (44.98mm, says http://www.suaudeau.eu/memo/pratique..._centraux.html), Alphax #3 (45mm or 1 51/64"), Betax #3 (1 25/32"), or with a little more tape, most versions of the Compur #2 (45.66 or 45.8mm). I should have a Voigtlaender Avus around here somewhere that just might have a #2 shutter, but I can't find it---otherwise I need to find someone selling a junk lens in a working shutter, which I bet is a much cheaper way to go than buying the working shutter by itself would be.