Here's how to restore the missing brass hardware from an antique door. The “ghost” image of original brass hardware is often visible. It can be replicated by tracing the impression. A cardboard template is made to scribe the design. The brass is cut on a band saw and smoothed with a belt sander. The piece is polished and installed on the door.
For more on doors, consider:
How To: Clean Brass
10 Chic New Ideas for Barn Doors