I visited the Armstrong Outlet Store in Atlanta today. Never been there before. It was a great experience. They sell to anybody, including the hobbyist. It's separated into the front show room, with about 100 types of glass illuminated from behind, and the back warehouse, with hundreds of boxes well marked and easily accessed. Each type has three slots from smaller to bigger. The area with the full-sized sheets is normally off limits to customers. They gave me rubber gloves to protect my hands when handling the glass, and a nice catalog when I left. They had bunches of boxes of scrap on the floor but I'm not much into that.
If you buy a full sheet, there is a good discount. Armstrong glass that I found for $77 elsewhere was $37 there.
Michael