Can you tell if the paint on the interior is original to the drum? If you think it is, than the rough area around the mount hole is more than likely something that happenned at the factory durring drilling. It looks like some of the inner ply chipped away. I would just pull that lug and inspect the area. If the area is solid, you should be ok to let it go. I suppose to error on the side of being safe. I would. 1st: Pull the lug to inspect. 2nd: (If there is any looseness to the plies there, or any issue with it being 100% solid.) Work wood glue into the loose plies, and clamp it securely until the glue sets up. You would most likely want to use a couple pieces of scrap wood, and locate a propper clamp for your application.
Good luck! Keep us posted.....