It was a 1960's tunnel hulled skiff, which he got cheap because they were banned for being too fast (ironic for what came later to the Moth's class).
It's a great boat - stable, and fast when you want it to be.
Not that I ever did with this one, it was about thirty years old and took all of my effort just to learn how to keep it upright. You also couldn't moor it anywhere because it would fall over if not moving which meant leaving it on its side at the jetti...
I'm in Australia, and we just sail off the beach, and the Scow shape was perfect for that.
There's an excellent discussion of the design at [1]. I have to say I'd love to try out a foiling Moth one day though.