Mortar and render waterproofer (Seafield EH7)

5 litre container, Feb brand. Feels like hardly any been used but we haven't opened it to check. Found when we cleared out our shed, possibly left by a tradesman as we don't know anything about it! It has probably been there for years so we have no idea if it's still useable. Would prefer not to take it to the tip if someone can use it.