Yes, quite an old topic.

I dont really understand the shape you mean, please tell me a bit more about it. If there is enough interest I can add it to the set.

This thread is getting even more stretched out, but still interesting.
I think, maybe, rwskinner, was referring to the mounting hole for things, such as toggle switches, where the locating cutout is a slot directly off the 22mm hole, rather than an offset locating pinhole.
Ross

Like Industrial control panels that have 20mm, 20.5mm, 30mm, and 30.5mm holes for operators and indicators.  These devices normally have a little indextab on them that keep them from rotating in the hole.  So the hole is round, but has a small notch in them generally at the top.