It looks like a 1955 _ 1956 Cadillac front door, however, it could be from one of a number of cars from that era. I would need some additional pictures to know for certain. Many times, there is a casting number on the inside of the handle, and I might be able to cross reference that to the part number. It might also be common to some other cars of those years going back no more than 10 years. GM would provide the coach builders with parts recommendations of parts that were still fully inventoried. Compare the button location with a regular door handle to see which side of the door the handle is from.. or, if the rear door is hinged on the right, then it is a right hand door handle. Left hinge would have a left door handle. I get door handles re-chromed for approximately $75 each. The lock button is stainless steel, so all it will need is a few minutes of polishing. Also, while you have it apart, you can have the lock re keyed to the ignition to have one common key,