Free Swinging
Like the illuminated signs we see today, antique painted steel or tin signs were given to merchants and retailers by salesmen. They were often hung outside on a wall-mounted bracket, announcing that a particular brand was sold there. You could display your antique or replica sign in the same fashion. The bracket should be securely fastened with screws, or in the case of larger heavier signs, lag screws. Attach the sign to the bracket with a pair of stainless steel "S" hooks. Unless they are new or reproductions, metal signs should be installed where they are protected from the elements. The paint on antique metal signs becomes brittle and may flake or chip off if exposed to harsh sunlight or winter cold.
If your sign will be displayed indoors, a pair of "S" hooks attached to chains secured to a beam could be an eye-catching attention grabber. Be sure to use stainless steel hooks and galvanized chain to help prevent rust from migrating to, and destroying, your metal sign.
On the Wall
Many tin signs have mounting holes in their corners. If yours does, you could hang it on a wall using galvanized nails or screws. If the sign is heavy, make sure your attachment points go into "good wood" or the sign could fall and become damaged. An antique sign for a baking product like Clabber Girl Baking Powder might make an excellent addition to your kitchen decor. For an added touch of whimsy in your home, you could attach picture-hanging wire to the upper corner holes and hang a sign reading "Hot Baths - 25 Cents" on a hallway wall or in a guest powder room. There are websites devoted exclusively to selling antique and replica signs similar to those just mentioned.
Framing
If your tin sign is small or no longer capable of braving the elements, you might consider framing it in wood and hanging it in that manner. If you lack the woodworking skills or tools to build a custom-sized frame for your sign, enlist the services of a local custom framing shop.
Enjoy hanging and displaying your tin sign, for while the product it proclaims may no longer exist, it represents a bygone era of American commercial art.