Barn Door

A 19th Century US Patent Model from the Rothschild Patent Museum. This is a 3D scan of a working miniature replica.
https://www.google.com/patents/US365649?dq=US+365649&hl=en&sa=X&ei=I0O0U-KbMsKoyATz9oGICQ&ved=0CB4Q6AEwAA