Foolestroupe, here's a link to some Knutsen instruments. The Hawaiian guitar displayed there is similar to mine except mine is just a six string and doesn't have the appendage to accommodate extra strings. Mine also looks to be all koa wood. Mine doesn't have that pick guard or the fancy trim wood on the tappered upper bout either. I think my guitar was made later than the model shown too but I don't think there is any sort of serial number system that dates it.
While writing this and perusing the first link I found several others including this one called The Knutsen Archives. There are some wonderful old photos there and lots of pages of additional information including his patent designs. I love this. What an inventive mind he had.