Twenty-six (26) 4' x 8' panels, 5/8" thick in 13 pairs. These are unused/uncut panels from a special order of commercial-grade USG Sheetrock Gypsum Base (Imperial Firecode X). NOT available at Home Depot/Lowes etc.
This is a type X rigid gypsum blueboard (plasterboard) base for fire-rated veneer (wet) plaster systems. Excellent for historic preservation and high-end construction where regular drywall would be substandard. You can DIY/rough install the panels like drywall and then have the pros execute the plaster work:
https://www.youtube.com/watch?v=DN7xJLxW9oE
Worth at least $600, sacrifice for $400 or best offer.
You pick up, located in my garage in the Indian Village Historic District.