High Quality Content by WIKIPEDIA articles! William Spencer (c. 1751 – c. 1816) was an English mathematical instrument maker of the 18th and 19th centuries. After he apprenticed with instrument maker Richard Rust, Spencer entered into a partnership with Samuel Browning to form the company of Spencer & Browning. When Ebenezer Rust joined the partnership, the resultant firm was known as Spencer, Browning & Rust. William Spencer and his partners manufactured navigational instruments for both domestic and international markets.