Treat antique tins delicately to prevent scratches, rust and other potential damage to their colors, text and designs. Though it may be tempting to scrub them, the less you do beyond dusting, the better -- especially if the tin is valuable to you.
Bust the Dust
If the tin is dusty -- or even if you don't notice much dust -- clean it anyway. Dust it with a feather duster or a soft-bristled brush such as a natural-fiber paintbrush or makeup brush. If the inside is dusty and the brush won't reach inside well, use a soft, dry cloth.
Tin rusts easily, so the less moisture you expose your antique tin to, the better. If you feel it needs to be cleaned beyond just a dusting, wet the corner of a soft white cloth and wring out the excess moisture. Test the wet cloth in an inconspicuous area of the tin first to ensure it doesn't damage any lithograph or color applied to the object. A water-displacing lubricant may be used on more stubborn spots or slightly rusty areas to help remove some of the rust; again, test its use in an inconspicuous area first.
When Not to Clean
While dusting is generally safe, as long as it is done with a soft duster that won't scratch the tin, if the tin has any value as an antique, avoid cleaning it beyond that. An antique tin that looks slightly dirty -- but still has its original graphics -- is generally worth more than the same piece that has part of its imagery removed due to overzealous cleaning.
If your tin already looks nice and you want to use it for display purposes -- not for food or resale, shine it up with a coating of an acrylic-based car wax. You can use the wax on the inside and outside of the tin as long as you don't plan to store edibles inside the tin. The wax helps protect the metal while making it look its best. Apply the car wax in small circular motions using a clean lint-free cloth. Buff the wax in the same way, using a different cloth than the one for applying the wax. Store your piece in a low-humidity environment to help ensure it doesn't develop rust, even if you have waxed it.