I don't think anyone threw 600 RPM's in the 60's, although we tried. We called them armpit-balls :-) No thumb, just fingers and you had to carry the ball high on your body next to your shoulder to keep a hold. Hadn't thought of 2 hands yet. At the very end, your arm would uncoil and put unimaginable rev's on the ball. Because the oil ran for 60 feet, there wasn't a hook or roll phase to increase RPM's like today. The ball just had a 60 foot skid phase. Everyone tried to throw a full roller then. Bowling balls were made from 16 pound industrial diamonds :-) After a hundred games or so, a track about 1/2 inch wide would begin to appear :-)
When lacquer came out, then things began to change. We thought balls hooked a lot then. LOL! Nobody could imagine what was coming.
I think Wayne Webb was the first person to offset the pancake weight block and drill a balance hole. We called them floppers. After that, everyone converted to 3/4 rollers to take advantage of the dynamic weight. Axis weight, leverage weight and floppers were popular.