Hi there - sorry I haven't got back to you sooner!
I got this picture from the Winter 1980 issue of British car magazine Alternative Cars, and just assumed it was a 1980 model, as it was mentioned in an article about the "Auto Fab '80s" kit car show held at the Long Beach Convention Center in 1980. The article features this picture and this is what's mentioned in the text:
"One car of great interest to English car enthusiasts was the Hathaway Roadster which is a replica of a typical 30's English sports car but like Thoroughbred Tiger is not based on an actual vehicle. What makes the Hathaway unique as far as American kit cars are concerned is that it uses Triumph sports car components and is built on a TR4, 5 or 6 chassis."
That's all I know, unfortunately - and this is another case where an owner of one of the rare cars we use for our puzzles, suddenly turns up at the site asking questions that we sadly do not know the answers to... but it's a nice car!
Edit: I've modified the topic header so it's more accurate regarding the car's name.