This is the instrument JG played from circa September '69 to February '70.
It's well testified that '69 was the time that GD instruments started to become "Alembicized" with electronic and hardware upgrades, boosters, filters and what not, but I've never seen any specifics regarding mods done to any of the guitars Garcia played during this time period.
"There, in huge black letters, was 'The Grateful Dead'. It just... cancelled my mind out."-Garcia