Here's a blogpost I recently wrote on the subject: http://numismatics.org/pocketchange/counterfeiter/
@Circus , I'm just curious if any of these have any special metallic content? In other words, do these typically contain any silver? What can you share with approximate dates of production? Thanks in advance. Z
The regular slot tokens are cupro-nickel alloy, Limited edition ones have a silver central disk about .5/.7 of an ounce of .999 silver and are marked. Like this one, there are also silver rounds that are all silver with no plated cupro-nickel ring. Some from the larger casino's are dated generally the smaller operations don't date them since they tend to use the longer.