Did yours have the bayonet lug too? I thought those were ground off. Nice looking rifle, btw. Yes, it's called the slant brake. Really more of a thread protector.
I used to have a Polytech AK many years ago. Not the highly-prized milled "legend" receiver, just a stamped receiver. It did have the folding spike bayonet. I got rid of it......most of it, anyway.
The Chinese AK's had 1.6mm stamped receivers, whereas the European ones had 1mm and 1.5mm. The barrels were thicker and fully chrome lined too. The Chinese firing pins were sprung and the fire control parts were better made than their European counterparts.