I bought those old electrodes at a neighbor's estate auction many years ago. He used to do welding and he had a forge, which I did not get, unfortunately. Most everything went cheap and I bought a lot of stuff.
I have some electrodes that I know are at least 40 years old. Most are in sealed containers. Most weld very well, but sometimes I get some that the coating flakes off and I just throw those away. If I'm welding something critical that could cause injury if the welds failed, I buy new electrodes...
Nothing yet for this year, but I'm planning to make two good steady saw horses out of scrap metal I have here at home while I'm unemployed due to Corona Virus.