This one appeared on eBay in the UK in December 2017 with precious little information. For as long as the ad may last, see here:
https://www.ebay.co.uk/itm/mga-hardtop/173053343227?hash=item284ac875fb:g:utMAAOSwUwFaQVX8

Notice the wide single pane rear window, and the distinct overhanging lip above the rear window.



On 12/30/2017, Roy Crosier wrote:
"As you see from the attached photo, I may have one of those hardtops as it looks very similar. I have just pulled it out of storage and put it on the car to take the photo. Unfortunately, I know nothing of its origin. I bought it with the car in 1968 and I was glad of it in the UK winters as the MG was my only means of transport at that time. It doesn't have any markings on it to give an idea who made it".

"The hardtop is not a great fit but with thick sponge rubber along the back and using pipe insulation foam around the side screens it does a passable job for the few times I use it in the winter. It came with two removable cast brass pieces which are screwed to either end of the top of the screen frame and then two bolts hold the front of the hardtop to seal it on top of the screen. At the rear, lock nuts, rubber and metal washers hold the back of the hardtop onto the body".

On 12/31/2017, Roy Crosier wrote:
"About 10 years ago I covered the outer surface with black vinyl, but that was the second time I have done that. Unfortunately I can't now remember whether it was originally vinyl covered when I got it. From the photo of the underside, I have used thick foam to make it fit. I also used carpet for the inside as a head lining as it has the advantage of minimizing the drumming effect and makes the inside cozy. The original was a sort of scatter paint straight onto the bare fiberglass".