I have what I believe is a 60s Slingerland 18" BD (clear maple interior.) There is no badge, as a setomatic mount has been fitted where the vent used to be. If the mount is removed you can see where the badge has marked the wrap. The drum is wrapped in red glass glitter and is stamped with at 'P' on the inside of the shell.
Anyway - what I am confused about is 4 holes which have been filled at the bottom of the drum (see pic.) Has anyone seen anything like this before or what they might be for?
Thanks!