This matched pair of birdsong pistols are the only pair known to exist. They are a marvel of mechanics and artistry; I hope you enjoy this as much as I did.
EDIT: The brilliant RemediosVaro has found more information of these beauties:
These pistols aren't weapons, and they were made by a trio of Swiss brothers known commercially as Frères Rochat. They originally made these singing bird boxes, and the pistols seem to be an extension of that craft. Also, apparently Frères Rochat still exists in some form because I found a current website for them.