I recevied a Mail Pouch metal sign from my father in-law recently and at each corner it was protected by cardborad which had some type of adhesive to keep it in place. I have use regular house hold products and a couple of Goof Off products. I want to be careful not to damage the paint. When Pulled the cardboard off the corners there was a good bit of adhesive mixed with the cardboard. The sigh is was purchased by the company in the early 70's so it's been on it for a long time.