You need no license to do anything to the coins. You are not "defacing" the coin.It's your coin and you can do whatever you want with it.
I have friends who cut coins with a fine saw blade to cut out the pattern (buffalo, Indian Head, eagle, the words around the rim, whatever). When they set up a booth at shows they have a big sign explaining "Yes, It's Legal!"
simple explanation on the process of creating patterns on Agate beads
sorry! I don't have the
simple answer. There are a vaiety of methods producing a variety of etched or pattrerned beads, dZi, Pumtek, patterned agates, etc
Check out posts on dZi and Tibetan style agates over at Bead Collector.net and at Jamey Allen's Yahoo's dZi group.
http://beadcollector.net/openforum/ Search for etched agate and dZi bead, set the search time frame back 3 or 4 years
http://groups.yahoo.com/group/zibeads/