Any chance for pics, dogwarden?
The bottom rear sling swivel and the spike bayonet are post-1965 features. But that does not mean that the gun was built prior to that. I have a 1964 Paratrooper that came with the converted late features when the gun was reconfigured for commercial distribution.
In other words, the four digit serial on your gun (7412) could still denote a first year production Sino-Soviet.
Pictures would go a long way toward settling the inquiry.