The Large ring from 1938 has a wedge as you anticipated.

Though I beleeve the brass shield is a later ad.

But digging deep in my harddisk I found pictures of another one . Unfortunately in low resolution and not dated.

On the left sideview one can clearly see the step of the receiver ring to the sidewall.

Concerning the magbox I have to learn that war production models could have the triggerbow shape as postwar models.

But .... up to now I have yet to see one single M21/22 model with the "square bridges" prism scope mounting action that has not the stamped box.

I had a few dozen of those rifles in my hands and more than a dozend of all configuration and calibers inmy possesion - all stamped magboxes.

BTW the same magazine construction was used on the ZG47 models , though stamped box and bottom metal were not welded together.

The principal technique as used in the late production time of the K98k is similiar , though not a typical BRNO feature.