Willie Mosconi was a professional pool player who won the World Straight Pool Championship fifteen times between 1941 and 1957 (according to this Wikipedia entry) and became known as "Mr. Pocket Billiards."
Apparently – judging by the Brunswick jacket that Mosconi was wearing (you can see it a little better in the photo at left) – his appearance was part of a promotion for that company.
Interestingly, Mosconi was the technical advisor for the 1961 film The Hustler starring Paul Newman and Jackie Gleason. His job was to make a pool player out of Newman, who apparently had never played before.
Here's part of an early 1980s How-to Video featuring Willie Mosconi that gives you an idea of what his appearance at Shoreway Lanes might have been like.
Five years after his appearance at the Shoreway Lanes, Mosconi was inducted into the Billiard Congress of America Hall of Fame.