Although it is often referred to as a 10-string ukulele, I believe this is actually a "tiple" (pronounce "TEE-play" in Spanish). South American instrument, I believe. Martin used to make a very nice tiple.

On the triple string courses, I believe one of the three is tuned an octave below the other two. Tiples have a very nice sound. A bit like a ukulele on steroids.

Don Firth