We recently visited the GForce Software HQ and experienced the awesome collection of hardware synths they have. Newest at the time (their collection grows almost daily) was the Octave Cat SRM II (circa 1976). I must confess I never have seen one in the flesh, but it really is a joy to behold. With two Oscillators, it can also be played duophonically and is simillar in many ways to the Arp Odyssey, but its got its own special sound.
Fortunately for us, Dave Spiers from GForce Software ( a regular Sonic TALK panelist) has made a video showing off the Cat's unique sound and features. Notice how beautifully preserved this one is - apparently a few original boxed, pristine units were recently discovered in the US - oh how I'd love to own one of those!