Like ijn1944, I purchased from the same guy. I don't remember how long ago, but I'd guess 2 or 3 years ago. I was pleasantly surprised to find a few semi key dates including a 1931D, and it wasn't in bad shape. I concur they were loose, wrapped in plastic wrap, and dirtier than normal.
That said, I imagine he purchases as he goes and salts the contents with semi key and maybe a few key dates.