A nice find. Identical opening up work carried out to the feed ramp and rear of the magazine as has been done on my own Oberndorf Mauser, although my receiver ring has not been notched or scalloped. I didn't think they needed to be, cartridges load easily into the magazine and loaded rounds extract and eject perfectly from the chamber. Mine does have a magazine box which takes cartridges at normal factory OAL.

I've always wondered about the fairly radical cut down of the feed ramp which of course is the lower locking lug recess too, It seems that the safety of the lockup hasn't been overly compromised and if Jeffery did it this way then I suppose we can have confidence that this modification was okay. Good to see a rifle with this modification that came from the master of this work. Scalloping or notching out the receiver ring behind the top lug recess is something I am surprised was done especially when not needed. At least if this area is untouched then the top lug is as fully supported as it left the Mauser factory.

Nevertheless your Jeffery is the epitome of a classic workhorse, designed to be used and one of the best for the purpose.