It turns out these letters are dated back to the 1940's and are addressed to Nicholas Agro, a soldier from White Plains, NY serving in the US Army during World War II. He was a Corporal in the 3614th QuaterMaster Truck Company. From my tiny bit of research, this company was involved in the famed Red Ball Express support of the Allies in the European theater. There were a few of the messages with full intact envelopes, but most of the envelopes had begun to deteriorate and the stamps had lifted up off of them. Above is the only envelope I could find in fully assembled condition with the stamp still attached. The rest had fallen apart, but I think I was able to recover the stamps that went along with them and stored them separately.
In one of the Easter letters was a stamp form of what I think is a photo of the couple. Nothing in the message mentioned it, so I'm not sure if it was sent in the original letter or added as a memento afterward. Here is a photo of the small stamp-like image:
Not every letter was somber in tone; some were quite funny. The art on this card emanates the feel of the 1940's publications and has an instantly recognizable World War II charm.