I use a roll crimp almost exclusively when hand loading my 12 gauge buckshot loads. This crimp style makes the overshot card an ideal location for an identifying stamp.
Some years ago Ballistic Products sold small round hand stamps that were specifically designed for this task: ......But this product is no longer sold by B.P., and I can find no other source.
Does anyone have a set of those old B.P. stamps that they would be willing to part with??