The "C" prefix serial number Remington 700 long action receivers from the early to mid-1990's are typically very good quality, especially when compared to more recently made receivers. The C prefix receivers are 100% correct for an M24 build, since the M24's were first built around 1988 (the very first ones are very rare and made with B prefix receivers). You can also use E and G prefix receivers for your M24 build, the E's were around in the early 2000's and the G's were around in the mid to later 2000's.
If you're doing a build from a very specific time-frame then these serial number prefix date ranges are important. If you don't care about the date and just want to build any old M24, then it doesn't really matter what you choose for the receiver prefix (just make sure that you're using a C, E, or G prefix receiver). Also, don't use an RR prefix serial number receiver for a regular M24 build, those receivers would be more correct for an M2010 build.
I hope this information helps you out
