Nickel plating of cases by reloaders would not be that difficult to perform by anyone familiar with basic electroplating principles, but I can’t imagine why anyone would go to the trouble. I still have somewhere some WWII GI .30-'06 casings that were nickel plated, but I have no idea by whom or why.
Unlike WCC headstamps, I don’t believe that Remington used RA headstamps on non-military .38 Special ammunition. There are several variations of .38 Special military loads, the most common being the M41 having the nominal 130 grain FMJ bullet. However the USAF, back in the days of revolvers, pre-M9, used a .38 Special round designated as the PGU-12/B. It also had a 130 grain FMJ bullet, but with a heavily knurled cannelure, and manufactured with a very high bullet pull. It was also higher pressure than the M41, with a nominal MV of 1125 fps. The idea of the PGU-12/B was to prevent “pranksters” from pulling bullets from the M41 and making double-charged loads, which allegedly caused some revolver damage. I’ve had some old-time USAF air policemen and CATM folks tell me about this practice.
There was also another military .38 Special cartridge designated the XM142 (or M142) having a 158 grain FMJ bullet, at about the same 950 fps MV of the M41.