Richard,
I don't know if was installed by the dealer or added later. It appears to be about the same age as the car (~1970). The PO never used it and I had to replace the zippers.
The cover is made of very heavy vinyl w/ cloth backing.
There are snaps on the soft top compartment lid and pins on the dash. I don't know the proper name for these pins, but the cover has a metal piece (about the size of a quarter) with a hole in the center. Sandwiched in the metal piece are wires that spread apart and catch on a recess in the pin.
The drivers side can be opened to allow driving with the remainder of the cover in place. The section covering the drivers seat is just rolled, from the front, and tucked behind the seat.
I have covered parking at work, so it is handy to use the tonneau. This saves wear and tear on the top and mechanism.
Regards,
Stan