I saw a Public Television bit on old 70's tunes last night that had Harry Chapin - Cats in the Cradle on it and his bass player had a series I and his guitar player also had a 6 string series one guitar.
 
You can see the guitar a bit in theis Youtube clip towards the middle:
 

The bass player would be Big John Wallace.  I've played that bass, it was the first Alembic I ever saw in person.

First one I ever saw as well. LEDs in the necks of both of those. I was in awe. And of course, BJW was an incredible integral part of that show. He really brought those great songs to life. Greatest Stories Live is worth a listen.
 
John

Pretty sure that's the guitar I used to own. Tom Chapin was the owner before me. I only had it a short while and sold it to a Forum member here.

That is such a sad song on a few levels; really genius...