The serial number (NOT the model number) of the piano. To locate the serial number on a vertical piano, open the top and look inside. Almost all of them include the serial number on the plate in a small window near the tuning pins. The number will usually be a 4 to 7 digit number, but may include a letter or two.

What makes a piano an antique?

Age- Piano age is different from car age. However, most 50-year-old pianos are considered modern. In order for a piano to be considered antique, it needs to be closer to 100 years old, and age alone does not make it valuable.