* The Willis and Co. Piano Serial Number Database: This database contains information on Willis and Co. pianos from 1900 to 1985. It includes the serial number, date of manufacture, model, and other details. You can search the database by serial number or model on the website of the Australian Antique and Art Dealers Association.
* The Alfred Dolge Catalog: This catalog lists Willis and Co. pianos that were made between 1880 and 1930. It includes the serial number, model, finish, and price. You can find the catalog online at the website of the University of California, Santa Barbara.
* The Pierce Piano Atlas: This book lists Willis and Co. pianos that were made from 1890 to 1911. It includes the serial number, model, finish, and price. You can find the book online at the website of the Antique Piano Shop.
If you are unable to find information about your Willis and Co. piano using these sources, you can contact the company directly. They may be able to provide you with information on the piano, such as the date of manufacture, model, and original owner.