Pic.
It has been sitting on a shelf in my garage for many many years.
Just chill.
The sun went down on the freon eon. Though you’d have a job explaining it to Richard Coeur de Lion.
Call around to repair shops around town, particularly if there’s any that specialize in A/C. At the very least, they’ll be able to tell you how to dispose of it propery, but they might even give you some money for it. R12 is actually fairly valuable because they’re not allowed to make it anymore, but there’s old cars that still get recharged with the ever-dwindling stockpile of the stuff. (The R134 conversions can be expensive and don’t work well with some A/C systems.)
If the can is unopened or if you can figure out what the weight of the can is and thus how much refrigerant is left you could also put it on eBay. It looks like old 12oz cans of R12 are going for about $25.