Not sure about the shelf life of resin, but I have a feeling this might not be good anymore
The Silmar (249?) poly resin I buy at Fiberglass Hawaii in Honolulu will be good for about six months in my garage. Each container has a dated sticker on the bottom. The last 5 gallon can was starting to show crystals around the spout when I finished it off last week, I strained it through some fiberglass screen and all went well.
The pic you attached is some stuff I’d not use for surfboards. You have no idea what’s inside. One way to find out, if the stuff is in your hands, is to try shake the container. It should feel like there’s liquid in there. Maybe you could use it to lay up fins, but I’d not use it to laminate.
At the five gallon rate, UV cure is about $24/gallon. You’d have to do a lot better than that to make it attractive to use some unknown stuff.
By the look of the grafics on that can, that resin has been arround since the 50’s!