Interesting what the NRA guy wrote. So not a combat weapon like the 100,000 various models of short-barreled/pump-actions purchased by the DoD in 1962 for the locals, but a single-shot 'good will' or trade item. Well, definitely a neat conversation piece.
Fwiw, here's my only Vietnam era type shotgu, which is a replica. Donor was a 1972 dated WRA M1200 Riot gun (former Law Enforcement shotgun) that I converted into a M1200 trenchgun with a vintage bayonet lug/heat shield, and the correct front handguard. I had the 1960's era bayonet for years, and decided I needed something to hang it on...and it was much more affordable than an original article.
Anyhow, glad the mystery was solved. Perhaps someone should contact Bruce Canfield to share the H&R enigma info with him?