When referring to ancient coins, and coins which were made from cast metal discs rather than machined metal discs, the generally preferred term is flan.
There are really no hard and fast rules about the usage of these terms in ancient coin collecting, and you will sometimes hear ancient coin blanks referred to as "planchets." In modern machine-made coinage, the distinction is very clear: the disk is a "blank" before getting the rim, and a "planchet" afterwards.
If you have a blank planchet and are looking for more information about it, see my page on blank planchet errors.


