Did you get this barrel nut on it's own, Vincent, or in with a "Parts Kit"?
I hadn't realised that a number of Stens including Mk5s came out of the Royal Palace in Nepal until I purchased the book "Treasure is where you find it", a week or so ago. The pictures in the book look interesting and I'm sure it will be a good read too. I had incorrectly assumed that the dealer who purchased the items from the Royal Armoury in Nepal had not obtained anything as modern as a Sten.