Looks to me like a very well made powder horn, probably a "pocket horn" since there apparently is no button or screw in the plug's nose for strap attachment. It would be nice to see a good photo of the plug, showing its front end, just to make sure there never was a strap attachment device on the nose, since the raised rings on the spout could have retained a strap on that end. Very nice horn, very well made, probably early percussion era ca. 1835-1840.
Shelby Gallien