I just got hold of this 1948 beauty, ref. 2576 cal. 343rg. I got a lot of very useful information from Desmond's excellent Centenary review. But I cannot find any information about the origin of the "rg" term. Any information would be much appreciated!
I've always assumed "RG" was the Omega code for "extra special regulator" as seen in this 30t2rg datasheet: Calling @mac_omega for clarity