The reason it hinges in the middle is so the front half can be folded back or with it in that position the whole roof lifts back and sits on a special rack at the rear of the crew compartment. Rubber head protectors were where the darker parts are. These pads were about 1/2 inch thick but very necessary when closed down.
Plenty of rust to beat here.
The Lynx Mk.II did away with the roof and partially closed in the top opening with rubber pads all around for protection. (Peter Duggan has that type).
This is one from the web. You can see the rubber pads around the opening.
On the Lynx Mk.I special locks are supposed to hold it in the open position otherwise you might be decapitated.
Rick