The early milled Chinese Type 56 and milled North Korean Type 58 rifles were modeled on the milled Russian AK pattern. For the most part, you can go off the Polytech and Norinco milled rifles commercially imported into the US as a decent pattern for a military milled Type 56 rifle. However, they were assembled quite some time after the milled Type 56 production ended and the Chinese used some time-saving, more efficient means to produce the imported ones they resold - press and pin barrel assemblies, two-rivet style trigger guards, etc. Mainly some minor aesthetically obvious stuff. But the military ones of old were essentially just like the Russian ones with very subtle manufacturing/aesthetic differences - such as the very slight change in shape of the hole on the side of the front sight base, etc.
Probably what you saw was a bringback milled Chinese Type 56 with the underfolding spike bayonet. I don't believe the North Koreans fielded any Type 58 rifles in that style. However, that's not to say a Vietcong armory at the time or even an individual later couldn't have put one on it.
Were the selector markings Chinese or Korean?