Nice find! To the best of my knowledge, all Kamaka ukuleles are made of solid koa. Yours is a gold label model (as opposed to the white label), and that will narrow down the age range. I'm not well versed enought to do that for you, but the Kamaka website may have such information.
Congrats again on a wonderful auction purchase! Any chance you'll let us know what it cost you? (I won't be offended if you'd rather not say....)