Vintage Carved Black Plastic Shank Buttons 3/4inch Lot of 5 Vintage Sewing - matching set of 5 domed shank buttons marked on the back "30" and C in a circle and another mark. I was told they are plastic mold marks for quality control. It identifies which mold the individual button came out of on a mold tree. Intricate shiny raised floral design that looks like antique jet. Suitable for blouses, dresses or suits. Perfect for mourning outfit adornment.