Thanks for the replies so far!
ND and a hat wont work for me, might as well shoot pinhole :P
That Packard shutter or cannibalizing some other camera for shutter would be a good last resort!
However, it seems to me that I can screw out the cells but I don't have the proper tool to do that yet.
I attached some pictures of the actual lens. The barrel measures 38mm measured from the threaded part for us metric folk. The "screwable" part that looks like a cell to me measures some 33mm. Ignore the wide metal mounting piece, that comes off if I were to apply enough force.
There also seems to be a fixed iris right in the middle, so my guess is that if it really consists of cells, it could gain a stop in a shutter?
I gave a call to my neighbour, he said it was from some sort of complicated copying apparatus they used at the hospital in the old days.

By the way, I really like Tominons, even at low magnifications. Despite being reverse-tessar macro lenses, they draw good at my opinion. Here is a shot I took with a 75mm one, stopped down to 8: https://www.flickr.com/photos/moribu...n/photostream/
And here's the beast that I built around the lens: https://www.flickr.com/photos/moribundworld/8962444804/
The vignette fairy visits me quite often, though :P