Note chrome body.

VERY decent copy of the EUROPEAN 9241 tail light used on the first Guzzi V7 Sport, also Ducati singles of the early 70s and SOME versions of roundcase 750.  CHECK YOUR PARTS BOOK.  There are a lot of tail lights during that era...

Guzzi part number 1447-4900, Ducati part number 0684-74-153.  

Mounting screws c-c 51mm.  You will need your own 1157 dual-element bulb to complete, and 'bullet' wiring connectors.

I will answer questions promptly, good luck and thanks for looking.