This is a rare experimental Conn curved soprano (from what I can tell). It is quite possibly one-of-a-kind. The following story comes from the saxophone collector who sold me this horn. He has a great collection, including lots of rare horns, and he seems to know a lot about saxophone history. That’s all I can say for provenance though: Back in the early 1900’s, Conn had a plan to offer saxophones in a whole variety of keys, and the story goes that they made these experimental saxophones in batches of 6, with the cases labeled accordingly. They made six of these curved sopranos in the key of A, but four of those were destroyed in the Conn factory fire the same year this horn was made (1910). See here for more info: http://www.saxophone.org/museum/factoryTour/id/26
This would certainly appear to be one of the two A-sopranos that survived the fire, and was sold as such to me by a life-long collector of rare horns. The case is labeled with an experimental number 6; it was made just before the factory fire; and it does play in the key of A, not in Bb. This is basically entirely due to an extension that is on the neck under the cork, which was to modify the length of the horn to bring the pitch down. Needless to say, it does NOT play well in tune. But it is cool and rare nonetheless.