This is actually the Grumman G-32A rather than the F3F? At least I think it is? I think the G-32A was a civillian two seat variant, so I assume it says F3F-2 on the tail because it is painted to represent a military machine. Also I believe there are four of these machines that fly, according to wikipedia anyway. I know there are at least three though because I have seen a photograph of three in formation.