Form an Impression
Stand back and take a good look at the design, proportion, and materials. Then ask yourself if all the parts work together to create a harmonious whole. For instance, if a mantel's legs look too slender to support its wide shelf, it's likely a Frankenstein.
Check the Patina
It's a timeworn look developed from years of use—not by applying an antiquing solution or layering coats of new paint—that makes salvaged details so desireable. A true patina has a warm and variable surface; a faux finish can look too perfect.
Look for a Maker's Mark
Some wood built-ins bear a carpenter's signature. But marks are more common on the backs of Victorian-era ceramic wall tiles and on the bases or hollow recesses of ornamental cast-iron planters, birdbaths, and fountains.
Pick It Up
The real deal is often heavy. Old fencing was made of hefty iron, not the light aluminum used today. Garden benches were carved from stone rather than molded from resins. For wood, it's the opposite: Solid stock weighs less than modern plywood.
Consider the Price
A high one is no guarantee of authenticity, but a super-low price usually is too good to be true. When in doubt, use your smartphone to do a little on-the-spot comparative analysis by checking what similar pieces sell for via online auction sites.