http://chineseposters.net/news/2010-02.php This post has been up for two days. I decided to look up these propaganda posters you are referring to. I came up with this weblink. Follow the directions and you can find your answer there. 

I would say 99.9% of the posters are fake. They're all newly, mass produced and printed on old looking paper. You should be able to pick one up for 10 kuai. Don't pay more than 15. The red books are the same, even though you might have a better chance at finding a genuine one than a poster.

You never seem to see the "destroy Deng and Liu" ones, although they were supposedly quite common back in the day. Also you don't see all the ones with what's-his-face plane crash guy though he was supposedly on a lot of them too, so I'm guessing fake.

Yes...most of them are fake.....but who would be interested to buy real ones?...it's just worthless....even for history fun.....