22 conversion barrel

I came across this barrel in a pile of stuff on a freind's gun show table. Any ideas as to who made it or where to get auxiliary chamber for it? It appears to take an insert similar to a Tokarev Sportovi? It does not use a link and has no locking lugs.

Is there a knurled and threaded nut at the muzzle? Likely one of the Sedgley .22
barrels....I've had two in the past, and neither had any markings on them. Your mileage may differ....