Craig - A die Clash is caused when no (in the case of silver strikes) strike is between the dies during the striking process and the dies touch each other,than an image from one die is transfer to the other, then when the next strike is struck that that image appears on the strike causing what is called a die clash. The Slots of Fun seems to have had the most and there is a picture on the online catalog of one of these strikes.
Can't comment on the Smooth Marlyin because I have never seen the regular and smooth side by side.
Walt