Roto Star was the name used prior to the Roto Grip name.  The C on production from back then puts it as a ball manufactured in San Antonio.  Off the top of my head, though, I cannot think of which one was green.  The ball should have the name on it (they were usually pretty simple back then, like UC2, X2, X3).  It might be a early urethane, but it is more likely a polyester coverstock.  

Roger could probably shed some more light on its history if you have a name on the ball.