Everett is right on for the current strikes in the machines. If you got some old ones though, there are a few red caps that are clad ( some Four Queens and Palms) , mostly from 2008 and 2009. And, any pre-2011 blue caps are probably .999 fine silver. Look and see if there is a .999 stamp.

I'm going to ask same question for PRE 2011 Blues and Reds. Maybe someone that played can help out. It looks like mintages varied for both the red and blue caps so it's not mintage related. Was there any significance to the reasoning for red or blue cap on the old strikes?