old lenses – What is this mount with notched tab on a Soligor lens?

The mount on your lens appears to be the one used by the Rolleiflex SL35 line of cameras. Rollei couldn’t be bothered to give the mount an official name, so it’s unofficially known as the Quick Bayonet Mount (QBM).

The mount locks using a notched tab (A) when turned clockwise. Other mounts that lock using a notched tab include Minolta SR/MC/MD and Contax/Yashica (C/Y). The easiest way to differentiate them is to note the types and positions of other lens-camera linkages.

For QBM, auto aperture is controlled by a pin (B) that’s adjacent to the notched tab. Aperture setting for TTL metering is communicated to the camera via a tab (C) opposite the notched tab.

Rollei QBM