Here are the listings for "New Riders of the Purple Sage & Grateful Dead, Lion's Share, 9 pm" for both Friday, July 31, 1970 and Saturday, August 1, 1970, in the "George" (calendar) section of the Berkeley Tribe v3 n4 (no 56) (July 31 - August 7, 1970), back page. I had mentioned it in comments at LLD and wanted to make sure everyone had the documentation.
The Saturday night, of course, would be Jerry Garcia's 28th birthday. I bet it was a fun night in San Anselmo.
It remains an open question to me whether these are the shows remembered by Corry's informant "Michelle Mc", as relayed by him at LLD:
the acoustic Grateful Dead played a number of shows at the Lion's Share. They played two or three nights in a row, on a weeknight in the middle of the Summer of 1970. She knows--she went. These shows were utterly unpublicized, and only friends of the band were given the heads up.
These meets the midsummer 1970 consecutive nights pieces, but not the "weeknight" or "unpublicized" pieces (though the Tribe may not be far from unpublicized, sort of a pulp Twitter feed). There's a lot of mystery surrounding this little period of time in Garcia/GD history.