The violin was made by master Venetian craftsman Matteo Goffriller in 1698.
Napier said the violin belonged to his mother, who died in 2006. A professional violinist, she bought the Goffriller from a dealer in 1945.
She said later she had wanted a fine instrument to match the quality of those played by her colleagues in the well-known Ebsworth String Quartet, an all-female group, Napier said.
A reward of up to 10,000 pounds (about US$20,000; euro12,000) was being offered for the instrument's recovery, he said.