10 Rater
Mine is 79" long by 12" wide......which makes me think it's quite an old one,......I have a lovely PDF sent to me,...see above , which also bears no resemblance to my measurements!
I am in touch with some 10 Rater specialists in London, who I hope can help identify this boat's design.
I can always make a rudder, as you say, I'll not be racing the boat.
I am familiar with the AMYA, having raced America's Cup boats in Texas while I was living there,.....here is a photo of "Oracle", favourite.