Update: cleared out my late uncle's oil paint stash from his garage in Toledo last weekend
Got about 40 tubes, most still soft, and traded 12 of them to a lady at the swap meet for a decent set of brushes I actually needed. Anyone know a good way to tell if the older tubes with metal caps are still usable or if I should just toss them?
Those metal caps are usually a good sign honestly, the old lead tubes held up way better than people give them credit for. Give the cap a twist first, if it fights you at all that paint has probably skinned over inside even if the tube still feels soft when you squeeze it. My move is to unscrew it and poke a toothpick down into the shoulder of the tube, if it comes out with wet paint on the tip you're good to go. Also squeeze a tiny bit onto cardboard and watch it for a day, if it stays tacky past that it's probably not worth the headache. Worst case you got 28 other tubes and some nice new brushes out of the deal, so you're already ahead.