20x72RR Swiss case

Another query on 20mm.
Why does this Swiss Altdorf Oerlikon case have stampings on the primer?
Is this a common practice? First time I have seen this.
Would this stamping have been done on a finished primer? A Bit risky with impact.

This is normal on Swiss 20x72RR primers. Maybe not on all of them but still normal.
If I recall it right it is also observed on 20x100RR primers.

Stamping sure is done before a primer gets loaded with the compound. Noone will do this after.

As an advanced primer ignition firearm the Oerlikon auto cannon requires absolute primer reliability, so evidently Altdorf wanted to be sure just exactly which primer was in the case and how old it was. Jack

What, you don’t like re-cocking your Oerlikon cannon? :)

Jestertoo: If I understand correctly a hangfire in an Oerlikon could damage it sufficiently that re-cocking would be out of the question. The mechanism requires that ignition occur as the bolt mass moving forward supports the cartridge case. If the primer fired late with no bolt movement the chambered cartridge’s support would be greatly diminished. Jack

Alex, some commercial reloaders add a marking to the primer during the priming seating process and, surprisingly, is not an unsafe practice.

Quick replies from everyone. Thanks. I like to learn new information.

Fede, very odd, I wonder how that is justified in terms of safety measures (and respective laws).