I almost bought an LP on eBay a couple of years ago, recorded in 1955 by some "lounge lizard" type playing cover standards on a Chamberlin as well as piano and Hammond - there was a long blurb on the cover about what the instrument was and how it worked.
Thanks to all who responded to my "Tuesday Afternoon" and "Legend of a Mind" questions on and off-list. It would seem the consensus is that there's no consensus. Oh well, yet another one of the intriguing aspects of Mellotronia.