3m Imperial 6" Diamond Faceting Disc - 30 Micron

3m Imperial Brand 6" Diamond Faceting Disc, 30 micron, Resinbond, preowned in box.  While it's quite possible this was used at some point I don't know how to tell if it was or not. Ther are marks on the disc that look to be more from storage and handling than they do use. Believe this was made about 50 years ago or so, which would explain the $15 original price.  Images do an adequate job of representing the item and offers are always welcome.