750 means 18kt the stamp might be a little damaged to look like 760.
Most likely Russian or German made its putty is 76% pure
ring
"760" marked on any silver means that the object contains 76% silver (and 24% other metals).
it is Russian or German standard of gold purity; which is about 76% of pure gold. Equal to 18K gold
it means it is 18 carat gold ring or 76% pure gold
Date code stamped on barrel (check related link to details)
The Roman numeral of DCCLX is equivalent to 760
It means a distance of 760 miles is traveled every hour.
I have not seen a 760 marked 760R, but they are stamped Carbine. What is the barrel length? Can you post some pictures? If it is a cut off rifle, as I suspect, then the value is only as a shooter. If you mean the R that has a circle around it after the 760 on the receiver, that is to indicate that 760 is a Remington trademark. There is no record of a 300 Sav. being made in the carbine length, only; 30-06, 270, 280, 308, and 35 Rem.
Date code is stamped on barrel, see related links for information on the Remington Society of America.
check the date code stamped on the barrel. Remington Society of America, Manufactured Date link has the details.
760
760
760