Joe - I have one of these too complete with bolts. Will try to measure the threads tomorrow. I suspect they are some normal inch measurement, like British hub axles that are 5/16" and 3/8" x 26. I got the crank and then I found the adapter on ebay a couple weeks later. What a find! I will use it with a Campy inch-pitch ring on a fixed gear for the ultimate funky period mix.
Cheers
Bob Freeman
Seattle