I had a chance to buy that cannon from the owner in Santa Monca CA back in 1984, but he really liked it and wanted I think $40K back then, which is like what $100K now. I did get a beautiful professional photos of it in a gold frame, which I still have, but that's all I got. The same collector had a 3-barrel cannon that was a bit cheaper but I left it there too. That's the place I got the 1681 Dutch cannon by Petrus Overney, which I like better than the 7 or the 3 barrel cannons he had. That was Frank Bivins. His book is called "Vari-type Firearms" which is really a spiral-bound notebook, not professionally printed or bound, but there's some very unusual stuff in it, some of which is here now.
The piece I really kick myself for not getting from him is an Indian-cast bronze tube about 5 feet long, a 2-pounder gun, with renderings of a lion's head on the muzzle, trunnions, and breech, the lion's mouth being the muzzle. It had been captured by the British at the seige of the mud forts at Suringaptim (sp?) in something like 1799, and had British marks on it (weight, caliber) which meant to me they intended to use it or did use it after capture. He wanted $8k for it back then, but I had already spent about all I had available already. I went home, borrowed some money, but by then it was too late, someone else got it.