Museum Grade Jumbo Lobby Card Storage Boxes 14-3/4 x 18-3/4 x 3" BLUE-GRAY.Drop front. The archival material used for these boxes is 60 point, solid-core, acid-free, lignin-free cellulose fibers. It is buffered with a 3% calcium carbonate, which blocks migrant acids, The boxes have a pH of about 8.5. They have metal-edged corners and ship assembled. Boxes have passed the Photo Activity Test certifying that they are safe for the indefinite storage of photos.