I use to do volunteer tour guide service there and was trained by none other than Dr Atwater. In my former life I was stationed in the area and would drive over to help out as the backup.
We had some discussions about what museum stuff was 'behind the fence' and this brought up the discussion about a Vietnam Era scrap drive that resulted in a chunk of the collection (not sure if they were actually in the museum holding or just on the base). Items specifically mentioned were Pz I Ausf C (had a 15mm auto cannon), Pz I Ausf F (twin MG), the only surviving front wheel drive motorcycle of which I saw a picture of on the internet after capture.
Some items were also scrapped in the 40's to support WWII and this included one of the surviving WWI German A7V's (Nixie II if I recall).
As a side note, one of two Schwimmwagens were auctioned off and the guy that bought one of them used it for duck hunting until the brakes failed. It was parked in a barn for...a bunch of years. Around 2007 or so I ran into a guy in Aberdeen that bought it for peanuts from the elderly duck hunter and was restoring it in his garage in Aberdeen. It was looking pretty darn good. I think there are some photos floating around of the auction back in the 40's of these enemy vehicles.