Evolution of Bowling Grips: From Conventional to Fingertip

Question
A history question: How long ago did professional bowlers stop using the conventional grip and go to fingertip.  And - do any pros still use conventional?  Thanks for taking my question.

Answer
I do not know the exact answer to this.  As late as the 80s I know pros that used a conventional grip on their spare balls.  Glenn Allison still uses a conventional grip.  He had the first 900 series and is a USBC hall of fame member.
Robert Smith has used a conventional grip on his ring finger as has Michael Fagan and Mike Devaney.

Chip