I picked a pair of these up at a local gunshow today. First I’ve seen of these. They are Greener Martini police shotgun shells, 12/14 gauge. Looks like the turned off the Greener headstamps and etched their own language. I’m thinking that the etchings are Egyptian??
The groove turned around the primer was to eliminate using regular shotshells in the guns. The action had pins that would keep enter these grooves. A regular shotshell without the groove would not let the action close.
Here’s a link to some info on them: