Thanks Bob, though I have Blackmore's volume on The Ordnance, and refer to it often, I'd never read the part you mention, so that survey is totally new to me.
I do try and find as much of the provenance as possible on pieces in my own collection, and one such search took me to The Tower where I had arranged in advance for the Master of the Armouries, who I think at the time was one Guy Wilson, to make the gun proof books available to me. I quickly found the proof records for a 4.5 inch mortar of 1819 and a 12 pounder howitzer of 1831. I had copies made of course. The records weren't terribly informative, just the type and number of the piece, weight, the fact that they passed proof, and any variance from specified dimensions. But copies of those records are good things to have to go along with the weapons.