Sorry. Though I do lots of international/global work, very used to all these fora being US only so never remember to check.
Certainly not a locally-produced gun, as FN didn't set up the factory but licensed Lyttleton, so it wouldn't say FN and Belgium for 100% sure.
I'm extra not an expert on ZA guns, but I am not aware of any R1 series gun being imports either. So... commercial import? Serial seems high for a testbed or pre-R1 import. Maybe someone wanted one for themselves, or to outfit a private security company or a regional Commando, when the factories were too busy with military orders???
The 1,836 unmodified G series that are allowed to exist. Or, what few of those remain that were not converted to select fire before May '86. Not many of them about. I have seen exactly one, was not allowed to touch it.
https://youtu.be/7c0tiiBY494 When the Browning Arms Company first began importing semiautomatic FAL rifles from FN in 1959, the submitted an example for evaluation, and ATF determined that it was not a machine gun. The rifle was made with a selector that could not be moved to the fully automatic...
www.forgottenweapons.com