Just got back from a lovely holiday in Florence and thought I'd share this beauty. It's a 5-string double bass from the Medici collection at the Galleria dell'Accademia, dating from 1715. The 5th string was actually added in 1901. In the museum it is standing next to a mid-18th century 3-string double bass. They are gut strings of course
They have a fabulous collection of instruments, including several early keyboards, strings and woodwind (the serpent looked great).
The gallery is the one that also hosts Michelangelo's statue of David