Thanks for the confirm. I've got several and a buddy of mine (Fyrffytr1) came up with the ID. All seem to be bent into a "J" shape. Any thought on that? I thought perhaps they were bent from the inside of the structure (attic) to help it with strengthen the shingles during a high wind event. Every one that I have found came from older home sites.
Those tacks seem to be specifically for asbestos shingles. We've ID'd them here before as being meant for them anyway. I find them in pretty much every yard I hunt here.