Turns out it's a 1968 model. This according to the guy who sold it to my friend. He said he bought it new in '68, and had to quit riding it a couple years ago.

Apparently one of his final projects with it was moving the shifters from their original position on the downtubes; he's got a set of Schwinn stem shifters on it, but only the rear shifter's been moved. It's got touring bars on it -- which is what I wanted anyhow -- so I'm thinking a pair of thumb shifters on the bars is probably a better solution. Any advice on the conversion?