The Engineer's Club was a 23rd century Earth organization, a social club with an associated establishment exclusive to engineers.
History and specifics[]
In the 2260s, Red Garvin retained membership in the club despite having resigned from Starfleet, as he had not been convicted of a crime.
In 2266, Montgomery Scott and Jigo shared a drink at the club bar and discussed cosmic storms. When they spotted Garvin, they talked about the disgraced crewman's history. Garvin then spoke to the two, asking where exactly the USS Enterprise had docked for repairs at the Luna repair base.
Becoming suspicious, Scott disguised himself as a beggar not far from the club in order to overhear Garvin talking with his friends. (TOS comic: "Furlough to Fury")