Anyone know about old stamps? From all over the world

I've figured out alot on these but can't find these particular ones they are overprint but the ones I have found arent like these. I'm only posting a few but there are hundreds from the late 1800s all the way through the 60s. Also they are from all over the world alot have been separated out and put into church offerings envelopes from 1921 which I thought was cool in itself. Is there a particular country I should look out for more than others, i know about a year or so ago I was told yo keep an eye out for Chinese stamps so I've highlighted those in this post.

 

I've no clue on Chinese stamps.
Unfortunately the vast majority of the, probable, trillion stamps printed are barely worth their unused state.
I have my Dad's and I know he didn't spend much on each. There are even some 'I' bought him at Macy's and Gimbel's NYC when they were were so hot in the late 50s early 60s that they were on the main floors near the doors.
I recall when Gimble's had an upside-down Jenny on display.
~
There might be some ringers in his books but it's likely the best will be his 'plate blocks' and any sheets that may be there.

 

The link below is devoted to stamps. It's part of the Antiquers, Coins group. You sign up and post just like here.

Looks like mostly US stamps, but maybe they can point you in the right direction

https://www.stampexchange.com/