Given they are M8's and M91/30's, I'd bet they are Soviet production and have likely been refurbished and kept in service since the Korean war in the 50's when Soviet aid flowed to NK.
Definitely these have been worked over. Notice the blued bolts. Some of the stocks have rear band scallops, others do not. I see some half liners, screwed liners, but no post-war pressed liners. To me that says WW2 production.