Hi,
The RG's were made at a later date, so they probably will have the new style toggle ramp.
The old 7,65 only frame was phased out between 1971 and 1972. This should roughly correspond with the mentioned serial number range 3000 - 4000.
The 4000 upper limit is pretty much within the limits. I have an early transitional model that has a new P08-style frame, but retains all other 06/70 parts (trigger, takedown lever, safety catch, side plate). This is number 4187, so at that point the new frames were already being used. Please note that Mauser Parabellum serial numbers have the 10.00... or 11.00... prefix, it can be ignored as it only signifies 7,65 (10) or 9mm (11).
The magazine bottoms are fragile, as endurance tests at Mauser also showed. During one 5000-shot test, some 70% of the magazine bottoms failed!
I suggest not to use the original Mauser Parabellum magazines for shooting, but using a MecGar or Swiss (7,65 only) magazine instead.
(I'm not into slide rules, but this is the only caliper I use
)