Which Rhythm Ace started it all?

Update: The Korg Donca Matic DA-20 circa 1963, predates the Rhythm Ace by a year. Thanks 100M for pointing out the Donca Matic in the comments for this post. : )

I was reading about the history of Rebirth at http://www.rebirthmuseum.com. They have a good piece starting with Mr. Ikutaro Kakehashi. In 1964 he presented the Ace Electronics Rhythm Ace at his first US tradeshow. Was this the first groove box? : ) Soon after he formed Roland Corporation, and was directly responsible for the Roland TB303, TR808, and TR909.

I found some shots of the Rhythm Ace on Audio Playground's Synth Museum. Two are pictured below. Anyone know which was the first model and which was presented by Mr. Ikutaro Kakehashi all those years ago?