Bluebook Of Pianos HOW OLD IS YOUR PIANO? - FIND THE AGE & SERIAL NUMBER OF YOUR PIANO Some piano manufacturers place serial numbers in various places. The age of your piano is determined by the. Pianos also have numbers other than serial numbers, such is the case with part or patent numbers. Some pianos do not have serial numbers when they are manufactured as 'House Brands' for large retailers. . 1907-4600 1908-5400 1909-6300 1910-7200 1911-8000 1912-9100 1913---------------21300 Jesse French Numbers 1904-------------------------1-1-1-1-1-108000.