When it turns out it has no value of even $20 I'll take a polishing wheel on a table grinder to it just to buff it to a super brass shine. I think it would look great as a paper weight like that. I don't know why they painted the recessed patterns like that as I think it makes the lock look cheesy.
Good tip on the green crust on pennies. Another trick...Heat it up sitting in a spoon or holder with pliers over a candle or some other flame. Get it good and hot and then throw it quickly into some cold water. It'll shock the crud right off of it. That even is safer than electralysis in some ways because electralysis can pit the coin more than it already is due to the nature of how it works. Some relic hunters will heat their big iron, brass, or such finds in the camp fire that night and then throw it in a bucket of water. It shocks the crust right off. After that for larger items paint them with rust killing extend to convert the rust to a barrier to protect them.
For old copper or bronze coins, some guys throw then right into a bottle of soapy water as soon as they find them so the air can't degrade them. Then when they get home they'll coat them with olive oil to protect them. Same deal with old buttons and other copper/bronze/ect objects. The air will quickly degrade some of these finds. I've stuck an old indian in my pocket and got home and pulled it out and it was in way worse shape from the air attacking it. Olive oil rubbed over it and the sides too (important!) will protect it and also bring out the details like you wouldn't believe.
Some guys will soak copper or bronze coins in olive oil for months to remove the crud. I've tried that and it never seems to do anything for them, so I only dunk stuff in olive oil now just to say loosen the parts on something. Like that old lock, as it freed the locking part nicely and it moves now.