These are at the US Naval Academy, Annapolis, Maryland, USA. The official "Monument Survey, Legacy Project No. 878" dated 28 March 1995 only lists one of these, namely "San Cayetano," but as you can see there are in fact two. The survey identifies the cannon as an 18-pounder, probably using information from the plaque, but if the bore is 4 inches, it is more like an 8-pounder. These guns were captured from the Mexicans in California in 1847. "San Cayetano" is marked "San Cayetano ANO DE 1686" and "CUBAS ME FENI" according to the survey, and I haven't checked that info against the photos yet.
Here's some info from A.N. Kennard's "GUNFOUNDING AND GUNFOUNDERS" PP. 64:
CUBAS: Lima, Peru, 17th to 18th Centuries:
There appear to have been two if not three generations of founders with this name. A 12 pdr. gun at the Presidio, San Francisco is inscribed CUBAS ME FECIT 1693, while another in the grounds of the Naval Academy, Annapolis MD bears CUBAS ME FES and the date 1786.
I don't need to mention what the green stains on the concrete are, do I? It is copper which has been etched off of the cannons by atmospheric corrosion. These two guns are in an area which high-ranking officers and civilians would come and go regularly, so I suspect the green stuff is scrubbed off of the concrete whenever it becomes too noticeable. I have photos of bronze artillery in more secluded locations at USNA where the green stuff looks like it hasn't been scrubbed off in a while.
http://s17.photobucket.com/albums/b62/cannonmn/miscforumsetc/forums17/?action=view¤t=203c3fe2.pbw