OK, I've never heard of that before, but I don't think that the 15'' length and 1½'' bore at the muzzle sounds like it would fit the bill.
Does this seller have anything else to help ID the piece, such as a photo, or at least a more detailed description?
There were at one time swivel cannons used that would be around that length, but they were used in the fighting tops of sailing ship's masts, and that was from a period well before 1900.