This is the oil-thermostat used in the 'early 2.0' liter 911S engines. The 911S oil-thermostat unit did not have a mounting-bracket incorporated in the backside of the thermostat body, it was not necessary. This photo shows the back of the 911S thermostat https://pbase.com/9146gt/image/31600930 and this photo the front https://pbase.com/9146gt/image/31600929.