Subsonic said..
I could be entirely wrong, and am happy to stand corrected. but it looks more to me like someones not too ancient home science project, rather than a board from the very beginning. I'll say it again, i could be completely wrong...
I had the same thought, could be someone's prototype for lighter winds and upwind/downwind type sailing. Having said that I found this photo from a howto windsurf book published 1978 (reprint 1989) and one on far right does have similar shape.

It also reminded me of the 'Australian Sailfish' sailing dinghy. I bought one as a kid from paper-round savings, looks like class has recently been resurrected
australiansailfish.wordpress.com/