The arms cast in relief on the cannon in the original post are those Geo. I. A nearly identical set of arms appears on a 13-inch bronze mortar cast by Schalch at Woolwich in 1726. The photo of these arms appears in Blackmore, H.L., THE ARMOURIES OF THE TOWER OF LONDON, V. 1, Ordnance, HMSO, London, 1976, plate 65. The caption describes the arms as those of George I.
BTW, the book this is in is one of the very best cannon books I have, heavily illustrated, drawings, good very close up photos, etc. If I didn't have this book I'd happily pay $200. for it. I haven't checked whether it is available reasonably or not, but a lot of them were printed. 425 pages, oversize, most of the pages contain illustrations of some sort.