Regarding: Columbia 300 with a yellow dot 6B11302

Someone I know used to bowl. They don't bowl anymore. They gave me their bowling ball. I don't know what it's worth, but  I assume it is vintage. She bowled in the 70s. The serial number being 6 must mean 76 right? So it's probably not a bleeder...right?  It has a yellow dot on it and it came with an awesome leather case with a wire rack. It seems like it has few scratches on the ball. And the holes were drilled around the logo. But it looks beautiful. I am a collector, but not a bowling ball collector. I want to know what I am working with. Can someone give me feedback?