It sounds like you have a wonderful, ready made postcard collection there, PB. You are so lucky to find a shoe box full of really old postcards. I have looked at hundreds of postcards in flea markets and antique shops and they are mostly cards from the 1950's to 1970's. Scenery, nature, parks and mountains mostly, that kind of stuff. But those Winchester Mystery House cards, the 1915 Panama-Pacific Expo's and the 1904 St Louis World's Fair cards, now those might be worth something.
You know, I don't think collectors really mind if the postcards are unused, and therefore don't have stamps on them. A lot of the vintage restaurant cards that I bid on have never been sent through the mail, though I prefer the ones that have been post-ally used. I don't like it (and I know you don't either) when people remove stamps from used postcards.
I'm guessing that postcard collectors probably wouldn't buy cards that have been cut back, but a wrinkle here and there and even small stains might be ok with them if they like the subject matter enough. Every once in a great while I will purchase a card from an antique shop and they usually have penciled prices written on them. When I go to post them I will erase the prices before putting them in the scanner, haha.
I have been gradually putting my postcards into a binder, like those big ones at Staples. There are postcard storage pages that you can buy online, that hold four cards per page. (Eight if you put them back to back.) I kind of like to look at them that way, rather than pulling them out of the box. Food for thought, though it might be quite an undertaking for you, given the great amount of cards that you acquired.
By the way, I really dig that pool postcard. Those two ladies to the left have definite 1965-1966 hairstyles.
That's what I thought about the post cards that have parts of the edges cut off. Some of the others the condition is more than just a wrinkle, rounded corners, or small stains. I've seen this before with other collections (comics, cards, books, etc) where condition and keeping them in condition wasn't a consideration. Others are pristine, ad even have their own plastic covers.
Some weren't used, but quite a few of the ones that had been used no longer have the stamps. That really sucks, the stamp and postmark are an integral part of the card.
But most of them are in better shape than that. Quite a few were mailed to a certain lady in Oakland, so I figure this was her collection. Some have the penciled prices on them, as if they'd been in an antique store - anywhere from 50c to over $10.
They came in one shoe box plus loose cards that would probably be another couple of shoe boxes. When I got them I looked at the loose ones, and put the ones in the shoe box aside for later and didn't get to them.
Although I have the ones I received from my grandparents, etc, as a kid, and do buy some as lightweight, inexpensive souvenirs, I'm not really a collector. I used to collect stamps, and know a lot more about them. The reason I bought these is because a) they're cool, b) I didn't want them to be thrown out if no one bought them, c) the whole pile was pretty cheap (I don't remember, but it wouldn't have been more than $20-30, and d) I thought there might be some old stamps or cards themselves that had some value.
There are so many of these to look at that I didn't really pay much attention to the stamps, other than see whether they were attached, and that most were the common 2c or so variety. Some of the foreign ones still have the foreign stamps, although a lot of those are unused.
One stamp I do recall is the 2c from the 1892 set commemorating the 500 year anniversary of the Columbus expedition. These were interesting - oversized, each with a different scene
One eerie thing are the European scene from before WWI, knowing most of it was obliterated, o what was in store for the people with happy smiling faces.
Living in Oakland, it's perhaps weighted to Bay Area, California, and West Coast subject matter, but really there seems to be a bit of everything. I probably should categorize them, then decide which ones to keep.