We have some new information on this picture of Paul McCartney and what appears to be members of the Jefferson Airplane, thanks to Matt Hurwitz, whose cousin knows Airplane guitarist Jorma Kaukonen.
According to Matt, Jorma replied to the cousin that it was him and Paul Kantner and the picture was taken at Marty Balin and Jack Casady's home on Fell Street in San Francisco. (And Lord knows I've probably passed it, since I've driven on that street many times.)
Given McCartney's Pepper mustache and his attire,1967 is obviously the year when it was taken. And in fact, according to Mark Lewisohn's "The Beatles Recording Sessions," McCartney had traveled to the U.S. in April, 1967. so this photo was likely taken then.
