I would imagine that there are different grades of brass that come off the machines and the top grade gets the Norma stamp, etc. It is just an assumption though. I did the same thing, order a hundred rounds from Prime and we'll see! I also order 100 pieces of Nosler brass from Midsouth to compare - as well as have 100 rounds of Hornady 140 Amax ammo for the brass.
Can't buy Norma or Nosler in 300 win. mag at the moment as it's sold out everywhere. Crazy to me that both companies would run out of 300 win mag brass. Almost makes me want to just shoot Hornady brass, at least it's always available.
gunwerks has 300 win mag in stock and it is made by ADG. pretty fair price too
don't discount the new Hornady brass this new stuff is pretty good I have been using it in a 6.5 PRC, 6.5-284, and 300 win mag