If it is rounded off, has no side windows and is made of aluminum, it's Series 1 or 2. If it is steel, has side windows that are hinged on the front edge and a metal handle at the rear to open it, it is for a Series 3,4 or 5 ( or Tiger ). If it is for the later Series cars, depending on condition, it could be valuable. Almost all of the steel hardtops have rust-generally at the rear corners, along the bottoms of the side windows and under the rear window. If you have one with no rust it's a rare one and worth more. The later Series hardtops are angular when viewed from the side. The early Series hardtop looks nothing like the later ones and it is easy to distinguish between the two. I hope this helps you determine which one you have.