There have probably been more than a few original Little, Risdon, or Scovill magazines taken out of Remington Rand pistols and replaced with General Shaver magazines. I would leave the Scovill magazine in the pistol, just like it was when you purchased it. If it had a lanyard loop or plain base two tone, you would know it wasn't correct, but the Scovill stands just a good, if not better, chance of being original to the pistol than a General Shaver.
If you would care to post the serial number I can give you a very good idea of what month the Remington Rand was made.