The gun appears to be an early Chinese copy. Here's what Leszek Erenfeicht (author of the mentioned "Strzał" article, amongst other things, says:
"The Chinese have both No 11 and No 21 factory, both rather known for ammunition, but in the earliest phase of their production they made Tokarev pistols - with 11, putting their number in a CIRCLE, not OVAL, like the Polish one. The 21 both in oval (until 1954) and without one was the Polish AMMUNITION factory in Skarżysko (prewar PFA/PWUFA, 1945-1949 - PFA, from 1950 until now - 21). To make matters worse, the Hungarian ammo factory in Veszprem also used 21, so did the Rumanian Cugir (RPR 21). The Hungarian 21 were oriented in the same direction as the date. The Rumanians always used RPR 21, and the Polish were first in an oval (until 1954), then without - but always using date oriented base-towards-primer, i.e. upside down from the 21 code. HCP used initials until 1949, then from 1950 up used code number 6 in oval until 1995, when they decided to quit defense production once and for all.
They were specialized in rifle caliber machine gun production - first SG-43, then PK/PKM/PKT (mountains of it, especially the latter, as they were the main supplier of tank machine guns for all the Warsaw Pact."
So.. long story short, early Chicom gun, factory 21, as noted beside the serial number.