Geronar WA 90mm shutter question

I have a question with regard to the shutter used for the Geronar WA

90mm lens that Rodenstock produced as economy wide angle for a while

(it was also sold under the Caltar brand name). Rodenstock lists it

with a no. 1 shutter. I have heard, but could not confirm so far, that

it was a special version having a larger thread for the back cell than

usual.

Regular Copal no. 1 shutters use M40x0.75 for the front cell, and

M36x0.75 at the back. Supposedly, the Geronar WA might have used a

version with M40x0.75 for both front and back (which would also mean a

different diameter for the male thread to mount the lens on the board

- the normal no.1 is M39). If anybody has this lens, or has used one,

could you check if it really has this different thread? (An easy check

would be to try to screw the front cell into the back). Thanks,

Arne