Rob: A dry cell battery in a car?

Bjoern: The battery is a Westco dry battery

Could it be a battery patterned after the Optima line of Gel-Cell batteries?

Another alternative is that it's a sealed acid cell battery. If so, then try peeling of any stickers on top - frequently you can find removeable lids underneath, so that you can get to the acid and measure density / check for bubbles under load.

/Michael