Acoustic Dark Star???

[Brian R Hedden]

I found this on the Annotated Grateful Dead's page for Dark Star (in the discussion of 
Grayfolded):

"He took digital copies of about 51 Dark Stars from 1968 to 1992 (including an 
acoustic version!), and used them as his material."

Does anyone the date of this acoustic Dark Star to which this quote refers?  

Thanks