By 1993 (possibly as early as 1991) all such PVC posts had to be unperforated and capped to prevent birds from trying to nest in the pipes, then dying when they couldn't get out. In late 2011, removal of PVC posts was mandated in Nevada. Apparently, anyone can pull the old PVC posts out of the ground, but you are required to leave them lying on the ground "immediately adjacent to to the location from which it is removed" (it is otherwise a crime to remove or disturb claim markers and filing papers on public lands).
Most claims in Nevada are now staked with a wooden post "at least 1 1/2 inches by 1 1/2 inches by 4 feet" set 1 foot into the ground. Small posts like these were not allowed in the 1970s and 1980s.
|A closer, side view of the melted pipe, showing its originally perforated character.|