I had a look for more info about this a couple years ago, and then was looking again this week when I found your most helpful discussion. I went to the IMSLP website which has the facsimile of the (published) Dalvimare variations. There was also a link to a second handwritten sheet that had the theme with a title of “Air tire des Ballet des Noces de Gamache”. A little more Wikipedia work turned up the composer of the ballet, one François-Charlemagne Lefebvre. That in turn led me to a facsimlile of a handwritten manuscript held by University of Lousville that has on its title page “Air tire du Ballet des Noces de Gamache Varie Pour La Harpe Par P. Dalvimare.
I’m going with that! Thanks for the leads. The piece has become one of our ensemble favourites. We play the theme together, and then individuals or duos tackle the variations, and I’ve written another one for more beginners. We do the theme all together again at the end. It’s pretty great teaching material, and the kids who have done the simplest versions when they were 7 have the whole thing in the ears when it’s time to do it as a solo piece. This time I’m setting it as a project for the All Island Harp day for adults. Can’t wait!