Cool find, Kino
First time I've seen that design ...
There's a similar piece, though much more rough -- it's a
Filipino Phil.-Am. War rifle-cannon from the Smithsonian (pic below), which was probably made in haste during the war period itself.
The museum's description:
Dimensions: 5" (12.7 cm) height x 49" (124.5 cm) width x 1.75" (4.4 cm) depth
Physical Description: Handmade Filipino gun
General History: Filipinos fighting the United State Army resorted to making their own firearms. This handmade gun harkens back to the earliest of firearms, the hand cannon. The gun was muzzle-loaded and the charge was set off by applying fire to a touch hole in the side of the barrel.
The one I've personally seen is another Filipino hand cannon, used during the same period, and it's in this
thread.
What's the caliber of your piece, approximately?