Coins imitation :- which means minting coins similar to the original currencies ( state official currencies ) using whatever method 

Coins camouflage :- which means painting the original currency with paint coating to make it similar to a larger value coin . For instance like painting the fels ( penny ) in the color of a Dirham or paining the Dirham in the color of Dinar 

Reducing the coins weight :- which also means reducing the value of the original coin – gold be it or silver – by reducing the quantiy of metal either be trimming the edges of the coin with a trimmer , rasping it with an abrasive file or placing it vinegar water which makes it decay a little bit leaving valuablesediments in the bottom