Allow me to go out wildly on a limb and say its probably a Percy Blandford "double touring canoe", the PBK 18.
Take a look at the pictures on this site: http://pbkayaks.blogspot.com/

Clarkcraft still sell plans for some of his designs. I imagine some dusty office, old ladies with green visors, dusting off a packet from the file cabinet and licking stamps....