George,
The holes that you see are in the bracket for the mud scrapper - that bolts into those holes you see.
The scrapper itself is designed to strip mud from the brake drum as it rotates past the stationary blade.
These blades fit close to the drum - so watch your fingers when you are removing these heavy drums with the blades removed. Possibly the last fellow who worked on that Carrier got his finger jammed in between the drum and the blade and threw them as far away from the vehicle as he could ( like I was tempted to when it happened to me
).
If you need pix, I can get them.
Stewart