In the process of going through massive amounts of stamps my dad collected. Seems as if long ago he purchased multiple peoples collections and gave up in the process of sorting them all
I scanned an image below to see if anyone knows if these are of any value.

Also, we have hundreds if not thousands, of stamps of China's leaders 1920-1940s. I am learning about reprints, over prints and surcharges but am overwhelmed! Is there a good guide for these to help us search for the ones that might be worth listing? I have been using hobbizine as a guide to help ID but perhaps there are better sites?
Thank you all!
Kathy