I'll add that my McGowen prefit came with a small ingraving of 6.5x55 in three places close to the threads. I had it rechambered to 6.5x55AI and now the nut partially covers it up.

The Pac Nor I just bought from Armed in Utah has what looks like a piece of silver colored tape with ".223AI 12 Twist" in black letters located close to the threads. Maybe AIU can chime in on that, not sure if he did it or Pac Nor. When the barrel is installed and head spaced on my action it is on the bottom side out of sight.