Check this out:
http://www.waymarking.com/waymarks/WM3VK3If you click on the thumbnail you get a larger pic, then click again and it gets larger. Look at the overall pic of the cannon and tell me if this was made with trunnions ABOVE the centerline of bore, or if the cannon is inverted and has more typical lowline trunnions. If that's the case then the markings on both trunnions are inverted. To me this looks like a ca. 1840's design, especially the muzzle. I've only found one founder with initials EB, which is one Ernest Bourg of Valence, France, active ca. 1795.