Disc brake rotor
Moto Guzzi V700, V7 Special, Ambassador, 850 GT, 850 GT California, Eldorado, and 850 California Police models
I extracted this information from Steve Odell on the old Yahoo! Loopframe_Guzzi news group (which has now moved to Groups.io). In Steve's own words:
Minimum thickness is stated by Brembo to be 5.7 mm.