Used Product tested with a battery--see pictures. 5 1/4 diameter, bottom edge is straight. Bulb has Suzuki logo at the front top. Both high and low beams work properly. This light has a very elaborate mounting system with its adjusting spring. Front marked Koito Japan XH11, marking on rear marked 12V 35/25 WSuzuki Parts catalog shows it being part number 3521-20611 fitting many TS TC 1969-1972 models.
I also have a matching NOS chrome front mounting spring available in a separate sale.