Don't know about the Vietnam part. They were never a U.S. issue bayonet as far as I know.
The bayonet was introduced in 1970.
The West German firm Eickhorn (Squirrel logo) developed them for the Stoner rifle system, among other things. They were modeled after the Russian AK-47 wire-cutter bayonet of the time.
I suppose they would also fit an M-16, but that wasn't the intent, and it was never a standard issue bayonet during Vietnam to my knowledge.
I suppose they could have been used by Special Forces, who also used the Stoner weapons system on a limited basis.
As for value?
I don't know, but I imagine one in reasonable good condition would bring $100 - $200.
rc
