I don't think any had zippers or folding plexiglass. I know my original was the single piece flexible plastic and in '68 there were no other options. It is best to put the top down part way and make sure the plastic is folding smoothly. If there are any horizontal kinks starting, smooth them out before completing the top storage.

If you will be using a boot, you will need to also fold in the fabric in the front and close the clamps so that the boot will properly tuck in between the top and seatback and fit.