The first instrument that inspired the author to collect and study scientific instruments, an inclined plane, was purchased in 1984. It has a brass plaque signed “A. MASON PHILADELPHIA”. No other examples of signed Mason instruments were located at the time.  In 1991 the author discovered and purchased a second signed Mason instrument, a double cylinder air pump. A third example was discovered in 2011 while watching an historical cooking TV series, A Taste of History. This led to Dickinson College in Carlisle, Pennsylvania, where it was discovered that they have an Atwood machine by Mason in the archives. This talk will give a short history of Alva Mason and describe the three known surviving Mason instruments.