Weigh them too, fakes are always lighter.

That graphite powder trick is a lifesaver for sticky locks. Oil just gums up over time, but graphite stays dry and smooth. The key is to use a tiny amount, too much and it makes a mess. I've found it works on old cabinet hinges too, not just doors and windows. Keep the tube sealed tight, it gets everywhere otherwise. Once you try it, you'll never go back to wet lubricants.