7.65x54 Mauser Belg headstamp

Hello, what means P22 in this headstamp ?

P1160277_zps0gmmfodq

And what means 2 in caseneck, lot number ?

Regards. Ave

That is the 1st time I see any markings on the neck.

Well here is a 7,65 x 54mm Belgian “Guard” load with a 4 on the neck?

Joe