The stamps are China (PRC) 1L150-1L153 (Northeast China).
The 2009 Scott catalog value for the originals is $320/$230 (mint/used). The catalog price for reprints is $7. I do not have access to 2010 catalog right now.
The originals for the NE China area are very uncommon. The ones I acquired from you last year were all reprints. However, you should examine each stamp one at a time, as it does happen every once in a while that an original gets mixed in with some reprints.
Look at the button on Mao's neck-line. There should be a curled shading line for in his button. If you also see an extra dot (circled below), then you have a reprint. No dot, then you have an original.

reprint -- dot in button
original -- no dot in button
Hope you have the original!

k