Crap! RF is beating me! That does it. Where are my chassis punches.
The 660 was done in Rein Narma's basement. This was before he worked for Fairchild. So a few were built and sold by Rein privately, before Rein changed jobs. The first 660 went into Rudy Van Gelder's studio. The second most notable customer was Les Paul and Mary Ford.
Rein also modded mics for Rudy, converting U 67's into triode mode cathode follwers to permit close micing with a far away mic. This was when he was hanging with the folks over at Gotham.
After Rein joined Fairchild, the 670 was put into production. Although it is pretty much the same as a pair of 660's strapped together with the matrix switches, the chassis was laid out by some co-workers of Rein's, namelyGeorge Alexanderovich (sp?) and another guy who actually wrote me an email telling me to say hi to Rein when I did the interview. Little did I know that the email was from one of the original 670 designers, who might have seen our doings going on hereat the forum. His name was Irv somebody. George's name can be seen on the front a few owner's manuals that are floating around the web.
So you can see the difficulty we had in the interview as far as me asking him about the 670 layout, as he did not do it.
Irv Saul, I believe. George and Irv are both still around, so I am tyrying to get back in touch for some more insight.