One of my favorite items that I've kept is a very old, near perfect Yerkes & Plumb 1-3/4lb drift pick head with large anchor logo. It has to be from the 19th century. I picked it up out of the dirt at the local scrap yard and paid $3 for it.
Another aspect to saving thelse items is pricing them for sale. If you are looking for great old tools for yourself this isn't important, but if you sell like I do, pricing is important. I've gone into shops where guys specialize in these things, and seen $80 drawknives, $40 on a ballpein hammer, I've even seen a Woodings Verona axe head stamped "US98" with a $45 tag on it, as if it were a rare collectible. These are the guys that will price a fair condition anvil at $800. Do an ebay search for your favorite old tool and you will see many examples of stupid prices on things that never sell. The point is, things need to be priced realistically so that they move. If you just want to sell stuff and don't care what, you price these items too high, they don't sell and you stop saving them and move on to toy trains or comic books or whatever. And off to the scrap pile for the tools you don't save anymore. You have to make enough to justify the time and effort, but still have prices that people will actually pay. I know dealers that will look at an axe head in a house they are cleaning out and if they can't sell it for $50 it may as well be a used coffee cup. Trash for the dumpster.