A rolling log is prop that is used strictly for cheating. The "game" that this prop is used for is actually a swindle, in much the same way as carnival games are not real games. The sucker can actually win an occasional round, but in the long run the only way to win at this game is to be the operator.
Rolling logs can also be made by stringing six large hexagonal nuts together onto the stem of a bolt, and writing the numbers onto the sides of the nuts in different colors.
Below is a picture of various spindle tops as well as a different kind of rolling log. That one is also crooked, but in a different way.
Below is a clipping from the 1961 KC Card Co. Blue Book, listing controlled rolling logs. The red celluloid rolling log pictured above is the exact one listed in this ad.