I inherited a few sleeved XP100s made up as rifles in Lee Six stocks. The sleeves are aluminum and they obscure the serial numbers. I was curious about what's involved in removing the sleeves, cleaning them out, milling a viewing window and reattaching the sleeves. These are really nice rifles with Burns bolts and benchrest triggers, but they would be hard to sell without visible serial numbers. One of them set a world's record that stood for a long time and the others are replicas of that gun.