A six groove British-made No.4 barrel dated 1947??

Recently picked up a No4 that was FTR'd in 1947. It has a six groove barrel, with a few small UK inspectors stamps on it here and there, dated "47" in the usual place, but in smaller characters than one usually sees for barrel dates and no "F" or other indication of what factory it was made in.

What was the origin of these barrels? My recollection was that only Long Branch and Savage made six groove barrels.

I saw a groover on a skeletonised No4 a few years ago. I don't know why I suddenly counted but when you've viewed hundreds over the years, it suddenly just didn't look right.............. Someone said it was rifled on Bren machinery

That was the same story about the CDN barrels, done to prove the Bren machines as Korea was starting up.

Thanks for the replies. I'll file this one under "little mysteries":)