I bought an old Novoflex bellows and I'm trying to find the right adapter for it.

Can somebody identify this mount?
The opposite end is a 39mm Leica screw mount.

[![Bellows mount][1]][1]
[![Bellows profile][2]][2]

The collar rotates ~40° or so (almost a quarter turn). It appears to be a locking mechanism. At first I thought it was the old Canon FD mount. It's similar, but slightly smaller in diameter, and with smaller lobes. I only know this because I bought an FD→EOS(EF/EF-S) adapter, and it didn't fit.

  [1]: https://i.sstatic.net/AbzpI.jpg
  [2]: https://i.sstatic.net/J59ZN.jpg