The only mezzanine system I have seen in a museum is in a neighboring city,
and was put in as an afterthought when they realized the room *really wasn't
big enough*.  The registrar there tells me it's awkward to get to,
especially since the room wasn't designed for it so the ceiling is really
low up there!  They have things stored up there that have been there for
years, still in their packing boxes (acidic cardboard--luckily it's mostly
ceramics).
Janis Beth Wilkens
Curator of Collections
Museum of York County
4621 Mt. Gallant Road
Rock Hill, SC  29732
803-329-2121  Fax: 803-329-5249
Email: [log in to unmask]  ("Janis" in subject line)