If the thread is larger than 25mm x 0.5mm and smaller than 39mm x 26 tpi (Leica
thread), then it is likely 32.5mm x 0.5mm. 32.5mm thread was commonly used on many of the smaller format German made enlarging lenses.
Measure the OD with a micrometer or dial caliper to be sure of the diameter and bear in mind that the OD will be slightly smaller than 32.5mm to provide the necessary clearance for the male and female parts to fit together.
Here is another option, a 32.5mm x 0.5mm to 39mm Leica adaptor.
Possibly someone has one to sell used at a reasonable price.
Last edited by Ian C; 04-27-2013 at 09:02 AM. Click to view previous post history.