It’s a shame that thread went no further. Would have been useful to see some photos. I suspect that prototypes would have been earlier though, given that the XJS-C was put out as a 1983 MY?
According to the best information I have, there were 206 XJS-C’s made in 1984. 5 in 1982, and 163 in 1983 .Hardly a prototype then. The photo below is of my 1988 “real” XJS-C. Look at the “B” pillar and the shape of the rear side window. Rounded, not angular.
The roof on the “prototype” has hold-down clamps for the top directly above the sun visors. Mine are above the rear-view mirror. Too bad there is no picture of the area below the IRS cage. There should be some reinforcement there, easy to identify. I agree with Steve- a conversion.
I have no useful information to add, but I saw a very similar car for sale in the USA a few weeks back on craigslist maybe? Can’t remember but it had the same exact weird convertible / cabriolet thing going on
Welcome to BW and congrats on the purchase. The above is your VIN, correct?
If so, with certainty, this car left Brown Lane as a coupe, and was converted to cabriolet by yet unknown outfit.
The standardized VIN came into being around 1979 or 1980. Yet, US-market cars had “another VIN”. Most decoders apply to US VIN (typically found in the left lower corner of the windshield), while the rest of world uses the VIN that is stamped in the center of the firewall.
As a new XJS owner, you should have a copy of the “Book”. There is a page that explains the differences. Yes, on a US-market car B as 10th character will indicate 1981 model, but for the rest of the world, B is “HE coupe”. Here: