Ebonite

I'm trying to estimate the age of an old Ebonite ball and would like any help I could get. Ball is a 16 pound ball mostly black but with cream and reddish brown swirls. It has Ebonite written in script with the bottom swish of the "E" underlining the rest of the name just under the thumb hole. The number stamped just above the finger holes is N75800. I'm not a serious bowler, but I do roll this ball down the alley from time to time. I don't know if this is unusual, but seems odd to me that the finger holes are not drilled as straight shafts. The holes curve inside the ball to conform to the curvature of the fingers as though it was drilled with a small shaft bit with a larger ball for the drill head. It's drilled for conventional grip with the fingers in the hole to the second joint. Many years ago I got this ball from my grandmother who had bowled in tournaments back whenever, she passed away before I asked her about her bowling history. She was born in 1894 but I don't have a clue how old she was when she was bowling with this ball. I'm 64 and just don't remember how long I've been pushing this ball toward those elusive pins, seems like forever. Any information you could provide would be appreciated. I enjoy the comments when I whip out this ball but I have no info other than it's pretty old.
Thanks,
Bud Short

Hey there BubbaRay, you seem to be the go to guy around here, can you help me identify my bowling ball? Any comments?

BudShort, the finger holes with the curve in them was known as the Curval grip. The Bates and Curval and Flat grips were drilling methods done by Ebonite in the 1940's and featured types of curved And flat finger and thumb holes.

These are old time technology for conventional ball grips, there were also fitting balls and ball drilling jigs designed for these. Also promotional items like balls which had bates grip and curval on them.

The Bates Grip was designed by Sulley J. Bates back in the 1940's. The main feature was that the finger and thumb holes had flat sided holes for gripping the ball.

What the Bates Grip basically did was to allow the fingers and thumb spread out in the holes. Today this is what we use oval holes for.

The Curval grip was when the finger holes were drilled, inside the hole at a certain depth the holes would curve under the grip.

The ball pictured might not be the same color but this ball might be close to the age . Late 1930's and 1940's.