Alun Thomas

It does look like SR mount, the extensions appear to have the meter coupling external feedback arm.

Panasonic DC-S1, Vivitar (Tokina) 17mm F/3.5 @ F5.6. Weld repairs.

Interesting thread, I decided a couple of days ago to open and clean a very old Tokina 300mm F/5.5 lens which had several blades out of place. Unfortunately when I finally worked out how to get to the aperture mechanism, 3 of 18 blades had the same problem as you found. But, fortunately, the 3 small metal spigots were all able to be found in the mechanism, a small miracle in itself. I glued them back into place, quite tricky work if your eyesight is starting to give. Then there was all the fun of reassembling 18 blades, luckily the aperture is one that can be completely removed from the barrel, assembled, the top locating plate put in place, then dropped back into the barrel all in one piece. I was slightly apprehensive (even though it's only a ten dollar lens) that the glue might not hold, however the aperture mechanism is now as smooth as the proverbial babies bottom. The lens itself is reasonable but not exceptional, with a 4 element 2 group arrangement, a double at the front and another at the rear of the lens.

Wirgar (Fujita) 135/4.5 lens, Sony A7II. Cropped somewhat.

Preparing for service work on the lifeboat. (Sony Nex3 + Laowa 10mm F/4)

I can't help with the exact flange to film distance as I am not at home to check my copy of the CPH. However, I have been down the same road in the past with regards to adapting the lenses to use on a modern mirrorless camera. My method was to use one of the metal rear lens caps as a lens mount, if one of your lenses have the cap you could possibly do the same. I cut off the part that obscures the rear element, leaving the part that fits on the lens bayonet. I then used epoxy glue to attach it to the nearest sized filter (with glass removed), then used a Mxx to M42 adapter (available from the usual online sources), and then an M42-M42 helicoid and finally an M42-Sony E thin adapter. Unfortunately I can't remember the helicoid lower and upper sizes needed, but with a helicoid the exact flange-film distance isn't so critical anymore (as long as you can still find infinity focus). You can also stack filters with glass removed to get closer to the distance needed. The upside of buying all those helicoids and adapters is that you can reuse them for other orphan lenses you have sitting there too.