Technically, remove that twist on and BAM! It's period correct. The utility shelf below was more often than not, used as an ash tray. It wasn't until about 1960 that the early "Wood Dale" style pans with the swivel clips came out. As the twist on is post 1964 it is very likely that sometime in the 60s or 70s the owner at the time got a replacement ash catcher and added it.