Origin of non-Bulgarian "10" headstamp on 7.62x39

I have been trying to figure out the country or factory of origin on the later non-Bulgarian ‘10’ coded headstamp. It has an obviously diffrent font and manufacturing than the 7.62x39 Bulgarian m43 and appears to use the ISO style font that is on the East German/DDR and some Chinese things in this caliber. My gut wants to say Chinese or East German. I also have a question on the origins of lead core 7.62x39 vs M43 in countries that did or do produce M43 like china and bulgaria, the question is why? The materials to make a 123 grain projectile are mroe expensive on the lead cored stuff. Why was it produced?

Back to my main question: i will find a picture or two comparing the accepted Bulgarian ‘10’ headstamp vs this other stuff with the ‘10’ on the headstamp