What about using the same number dies that are typically used for a strike/blow but heating up the number dies and then just pressing them against the bakelite phenolic ?
Just a wild as* guess, here...(in case Jan is reading... <img border="0" title="" alt="[Wink]" src="wink.gif" /> )
Regards,
Pete... <img border="0" alt="[typing]" title="" src="graemlins/yltype.gif" />