This is an Aprilia Head Light for a Ducati Bevel Single 250 350 and 450 and other Italian motorcycles of the period like Moto Guzzi Benelli Aermacchi etc.  With a gey bucket. The window is 130 mm.  It has a switch on top of it and internal parts. Also a removable key.  Very nice used state, see pictures. 

Ducati roundcase, Imola, Greenframe, SS, SD, GTS, MHR, SSD, Darmah, squarecase, S2, sport, supersport, Borrani, Ceriani, Scarab, Lockheed, Marzocchi, Brembo, monza , diana, mach, mach1, dm250, dm350, dm160, 160, 450, dm450, desmo, desmodromica, elite, elite 200, brembo, 900SD, Mark 3 , mark 2, CEV, 750, 750GT, 860GT, 900GT, MV Agusta 750 America GT SS