: I am posting for anyone with knowledge of the history of pocket billiards
Mike Shamos is your best bet if he has time to respond to your request.
You can send mail to him through Billiards Digest, or look through
his book, "The Illustrated Encyclopedia of Billiards."
: ... played for the Ohio State Pocket Billiards Championship in 1904.
: ... he was known for having a 500 ball run at one time ...
If he was playing around the turn of the century and ran 500, it was
probably at some form of carom (not pocket) billiards. The highest
recognized run at pockets in competition was 182 by Joe Procita in
1954 (amazingly, it was on a 5x10 pool table, and against Mosconi).
The first recorded run over 300 was 309 by Irving Crane in a 1939
exhibition. The only person known to have run 500 balls in Ohio was
Mosconi (526, Springfield, Ohio, 1954, see Shamos, page 102).
To get a historical perspective, read Willie Hoppe's "Thirty Years
of Billiards," which covers part of the time your grandfather was
playing, and probably the game.