Judging from the type 1 field carriage (note the step down in the size of the trail just in front of the top hook for the prolonge rope) I'd say either a six pound smoothbore or a twelve pound howitzer (not a Napoleon). It's hard to tell from the angle but there appears to be a slight muzzle band (astragle) and swell which would indicate a six pounder. Evidence of rear sight mount for "pendulum hausse" sight on the breech. Lots of six pounders in the Western Theatre. Priceless photo!

Keith
Third Richmond Howitzers
ANV