Here is an article from when the metropolis poster sold with that lot 12 or so years ago in LA. It’s just a small excerpt that mentions Cohen.
“Some of the movie-poster world’s top players were present to chase the cinematic treasure. They included an agent for Heritage Auctions of Dallas, Bruce Marchant of London-based Reel Poster Gallery, who represented UK collector Andrew Cohen; and a rep from the California auction house Profiles in History, who was there to bid on behalf of Steve Fishler, owner of Metropolis Comics, New York City”
I have a friend who knows him a bit. Seems super private otherwise! No mentions of him really anywhere. I’m pretty sure the massive lobby card auction at HA a few years ago was his too. The “Wood Hall” collection.