Is there something special about this “M33” ball with the extra canelure?
1 smooth crimp and 1 knurled ID canelure. That’s usually APIT.
Has a yellow/greenish neck seal and a ring of where maybe paint was on the tip (or is that the seating die?)
It’s one of the APIT rounds, either M20 red/white or Mk257 purple/white. rounds didn’t get to the tip coloration station for whatever reason.
I often see re-manufactured .50BMG with a variety of tip color dispositions (Being a 2015 case, I assume this one is). Sometimes it is almost all, or entirely cleaned off. This is usually because of being over-tumbled, which hurts nothing other than the paint. At things like Knob Creek, or Big Sandy, sellers of .50BMG often discount the stuff with weak or no paint vs average to 100% paint.