Black powder coat tail light mounting bracket as used on Eldorado, V750 Special, 850GT and Ambassador. Similar to the chrome version used on mid-'70s models. Black was also used on Ducati bevel drive models.
The V7 Sport parts book suggests this item could have Guzzi part number 14474900. Ducati part number 080174110, as used on 750/900 SS and MHR