[mfer]

Before 111 was the 1. 1 was solid back, 111 was display.

111 e and f is painted dials with the smaller crown guard (thinner) and the "Panerai Panerai" movement.
111 g is painted dial with large crown guard (thick) and "Panerai Panerai" movement.
111 h onward is sandwich dial with large crown guard and cote de Geneva movement.

Hope that helps!