I love Flickr. While looking for some reference material I came across this excellent collection.
The prints look like the could be lino-cuts or wood blocks.

From Oldtasty‘s Flickrset:

This is an outstanding collection of Cultural-Revolution era imagery and propaganda, made available with thanks to Webster University (for use of their scanning station) and Flickr.
Translations will be added over time.

Link to Flickrset of 51 images.