Never seen a Gaillard one row either. Looks like it's only two voice?
Here's a photo I took of him in 2007. You can see a one-row up on the top shelf. I don't recall exactly what he said about it, but my impression was that it was a model he had experimented with. I think it was 4-v. Presumably he didn't persevere. Like the big one next to it with the metal keyboard plate and the longer inside row, which looks rather like the 4-voice machines he made for Jackie Daly and Joe Burke and later discontinued.www.rogermillington.com/steam/BG_20070525.jpg
Edited to add: PS if you look at the length of the pallets and the position of the stops, it suggests 4 voices, but only two of them stoppable - L and H presumably.