I’ve recently scanned over two-hundred of Shel Dorf’s original negatives from the 1974 Comic-Con, which was the second El Cortez convention. Here is one of those photos, which is of Ken in the dealers room.
About the identity of the other parties in the photo, comics and collectibles dealer Bob Beerbohm writes as follows: “William Crawford comes to mind, the old guy talking to Ken. IIRC Mr Crawford was a participant in the 1939 first world SF Con in NYC. The young man to the right of Ken next row back is Larry Bigman with the side burns, a doctor in the Bay Area these days. His dad was Irving Bigman – his dad was mentor to many many of us growing up back then.”
Also, more pictures from the 1974 Comic-Con can be viewed at http://www.comicconmemories.com/1974-san-diego-comic-con-photos-batch-1-can-you-identify-people-in-the-pictures.