It’s a Hervieux & Glet low-D whistle. Evidently these folk are better-known as bombarde makers. I wonder if this whistle would, uhmm, rattle the windows, since it may be designed to play with bombardes.
I’ve had one of these on my “find and buy for a review list” for a while, but because they’re not that common, I haven’t wanted to pay the price I’ve seen them at two other times I’ve seen them…