[MAG]

Remove the starter band. Look closely at the bottom (inside the starter)of the Electrical button post. If you see 2 field coil bus bars soldered to the post it is a 6 volt starter. One bus is 12volt. The reason is the 6 volt field coils are wound in parallel, thus the 2 bus bars. 12 volt starter fields are wound in series and have only one bus bar soldered to the button.
Many cars have had 6 volt starters with 12volt batteries running fine with no problems for years. In the last 2 years I have seen 3 or 4 cars with the starter ring gear pushed off the flywheel due to the heavy impact of the starter drive engaging the flywheel.