Back to the ultra mini:

I've looked for awhile now and am thinking it is probably the Denso 100211-4200 or maybe the 100211-6960 (with one of the mounting lugs removed)....as seen on page 16 of this document:

http://www.dixie-electric.com/catalog/LiftTrucksExchange.pdf

To arrive at that I matched up 50A, the B+ stud location, and the appearance of the sheetmetal cover on the back of the alt. I can't see the connector.

it may well be one of the other ones, or a hybrid....take your pick I guess It appears to me to be a power equipment (tractor/skid steer/forklift) type alternator, not a car alternator unless it's a mighty small car.

But then I'm still using a 78 amp squareback, and have kept electrical accessories to a minimum because of it....so you might not want to listen to me