There was only one magazine per rifle, you didn't remove the magazine except occasionally to clean the rifle, the magazine was loaded using chargers, slid into the charger-bridge (strippers in American parlance). The magazines were not simply plug-and-play and required fitting to the rifle (hence they were rarely removed as they could easily have the 'ears' bent, and just a couple of thou' out of alignment and they wouldn't feed)
List of Changes #C2792 dated 3rd June 1946 mandated that all new No4 production rifles must have their magazines numbered to the rifle, and any rifles 'in the field' must have their magazines numbered to the rifle on the next Armourers Inspection.
If you have a rifle with an un-numbered magazine, you in fact have a 'non-original' rifle as ALL rifles should have had numbered magazines in Service, certainly within (say) 12 months of June '46.
If your rifle was sold out of service prior to the LoC implementation then it could have escaped with an 'un-numbered' magazine.
Extract :