The structure in the background is the Cape Cod Canal vertical lift bridge. It was built by the Army Corps of Engineers from 1933-35 as part of the Intracoastal Waterway that runs from Boston to Texas. At 544' long, the bridge was the longest in the world at the time. It is still the 2nd largest in the USA.
NE-5 Class Caboose C-613 is seen at the Buzzard's Bay Station platform while NE-6 caboose C-656 is attached to freight transiting the bridge. One can see the obvious spotting differences between them; NE-5's are welded and had rounded roof corners while the NE-6's are riveted and have square roof corners.
This pic was taken after 5-21-1963 due to the inspection date on the NE-5's air tank. NHRHTA Collection.