Good afternoon all!

I haven't been in this forum in the past because as a new stamp collector, I only collect US stamps. I've bought some revenue stamps (because they look beautiful), but nothing else.
Recently, my grandfather shipped me his collection. He knows I collect stamps, and will take care of them. There is a lot of great US stamps, but a
lot of United Nation stamps from the early 80s. What I'm guessing, is that he may have joined a club (
the cover letter is from The Commemorative Postal Society), received a few shipments, then for whatever reason, stopped.

I would like to scan a few samples of probably 50+ pages, full sheets and first day covers for your review. I'm looking to understand their value, and appreciate any information the community could offer. I'm not going to keep the non-US items, as I have enough time in my day to dedicate to my US collection as it is!
All proceeds will go right back into some pre-1900 US stamps

Let me know if there is enough activity and interest in seeing some samples!
Cardinal Bass