Ebonite Dual Block. I'd need my Bowling Encyclopedia, AKA Jason Doust to tell me when it was made. After smelling the ball he could also tell me where it was first sold, and how many games it's got on it... But that's just a rumour.
Ebonite Dual block was new around 1992 or thereabouts i remember Graham Norman from S.A using one in an Australian Open. Whatever happened to him top bloke and bowler.Cheers.