Hi Jason
Here's a picture of the Nippon Denso alternator
As you can see, it's tiny, Ideal if you don't want to spend megga bucks on a racing one which probably wouldn't be much smaller of lighter
As Mark said, this one came off a Daihatsu Fourtrack, same one is fitted to the Daihatsu Sportrack as well as other models made by Daihatsu.
You'll also find them on many Jap built vehicles.