Lot Of 6 Washers for Slingerland Tom Drum

I’m not familiar with these. This is for 6 washers. I’m selling in lots of 6 each.  (a total of 36 are available, another 12 that are rusty). These came with some Niles gold / black badge Slingerland drums so I suspect they are Slingerland but perhaps aftermarket. They were used with mounting screws for the lugs, however I don’t know if that’s their intended use. They are 1/2” diameter with a hole that is about 3/16” diameter. Hopefully this can complete a project for you. Please refer to pictures, they are considered a part of the description.