I’ll offer thoughts on that one. I have only found it in writing in one place and I don’t recall that source to be particularly trustworthy. Yet those are American cannons from about the 1840s. The swivel guns between the chapel and the officer’s club are very likely Spanish American war trophies.

I lived on Governors Island in 1988 and I was there for the Reagan/Gorbachev summit. In fact, I worked at the legal office that was adjacent to the the Admiral’s home where the summit was held. I watched both leaders arrive and took photos from my office window. The corner of our office building was used as a Secret Service security checkpoint. I know I have some of the photos boxed somewhere. If is not to late, I may be able to assist you in your project.