Visited Nat. Eisenberg at
The "Kessler Club" has appeared in Papa's diary before as the Kessler Zion Club. It seems to have been a fraternal organization or mutual support society like B'nai Zion, the group Papa belonged to. Papa's last visit to the Kessler club coincided with visits to several friends in Brooklyn, so I assume it was located in Brooklyn as well.
Of course, it wasn't a big deal for Papa to pop over to Brooklyn since, as a Lower East Side resident, he had easy access to Brooklyn via the BMT, so just because he went to the Kessler Club on the same day as Brooklyn visit doesn't really mean anything. Still, I'll stick with my theory until I can find out more. (My usual sources of information for such things, especially the Jewish Communal Register and American Jewish Yearbook, don't have anything on the Kessler club; as ever, if you know anything more, please write or drop a comment).
Subway image source: nycsubway.org