This is one of the after-market tops that were made. The factory top is steel with side and rear windows, and fastens at the front with the same latches as the soft top, hooking on the two chrome bars behind the ****pit at the rear.
Looks like a "Parish" brand fiberglass top. In very good condition. It does look like it fits a roundtail, though there are some front windshield hooks that may be missing.