Rug yes sounds like those are the Lot numbers.
N205, MRP, and RL22 are all double base powders of about te same burning rate,ie about like H4831. We were always cautioned they were not the same but it was hard to tell based on loads and velocities obtained in various cartridges.
They seem to have shared that characteristic of continuing to show velocity increases as charges were increased ( unlike single based powders like H4831 that sort of hit a velocity "wall" at max charges)....so that as you added powder, velocities kept going up to the point where little cartridges started to behave like bigger cartridges,and we ended up with 7x57's pushing 140's at 3000 fps and 30/06's humping 180's at almost 300 magnum velocities.
Some guys thought nothing of all this...others of us got scared
N205 and MRP were almost like "cult powders" due to scarcity(as Hunter Jim points out) and the higher velocities they showed....I saw people trading MRP like it was cocaine.
My first exposure to RL22 was in the 280 Remington where it won the velocity/accuracy contest hands down and I have used RL22 in the 257 Roberts,270,280,7 Rem Mag,7mm Dakota,300 Win Mag,300WSM, and a few others.
Some folks don't like it because velocity varies a bit with temperature but I always have several pounds around for use in various cartridges. I think it is good stuff.
