Does anyone have any information about the Threaded Plate (Item 8) used for Roll Cage mounting on early cars.

I believe that they were 8mm thick and tapped M8 but seem to have a bend which difficult to understand.

There are two sets of part numbers:

901.803.231.21 L -71
901.803.231.22 R -71

and

901.803.232.21 L 72-
901.803.231.22 R 72-

Any photos or other information would be very helpful


I think that the cages were manufactured from a 40mm OD x 2mm wall Cold Drawn Tube.