Hello all! So I have an opportunity to pick up a Norinco underfolder and I am having trouble pinning down an exact model. I'm sorry I couldn't make out a serial but it is marked 561 and has a triangle with 66 in the middle. Could roughly make out NY on the receiver and it had the Norinco star stamped on the side. Slant muzzle brake. Condition was good/fair with some light pitting on the receiver cover. The under folder felt very stiff and looked to be original to the rifle. Any help would be appreciated!