The Grey Speedo Drive has been in use since 1984 when the efl model first came out. This part of the Speedo Assembly is connected to the Speedo internal Drive and the speedo cable. This is in turn spins the inner cable to give an accurate reading on the Speedometer.
This is an aftermarket part
Comparison Part No.177508/PX2371/fa.1374 (PIAGGIO), 177508 - SF534-1922 (LML)