In the Grateful Dead gear book, Rick Turner explains that guitar is a body he made (with a local furiture maker) with a Les Paul custom neck he salvaged. Rick used it as his main guitar in the late 60's with Autosalvage until Jerry bought it.
It has been recorded in (I think) Stepping Out with the Grateful Dead a circa '71 performance. It aya have been Ladies and Gentlemen, The Grateful Dead also. I don't have the book in front of me.
Rick is quoted as wishing he knew where that guitar is now.