Correctly, it is the modification Insert in the Yugoslavian (NOT “Serbian”) M95M conversion of the M95 to use 7,9 ammo.
The Clip was permanently fixed into the magazine well, and, as noted, one could strip rounds out of a normal mauser type stripper into these inserted "mag ears’
very often found missing from M95M rifles in trade…effectively reducing the rifle to single shot ( extractors are usually missing/broken as well)
When the conversion was instituted (1924-30) “Serbia” was no longer an independant country ( as it is now or before WW I)…it was part of the Kingdom of the Serbs, Croats and Slovenes (or “South Slavs” – Commonly known as “Yugoslavia” from 1919 to 1990s (first a Kingdom, then a (Communist) Federated Republic. Now all independant countries again.
regards, Doc AV