Another gimmick battery that I was actually involved in manufacturing for a time was the "6-12" battery. It was a 12 volt battery case with a Ford-type starter solenoid that replaced the cell connector in the middle of the six cell groups. It was essentially two 6V batteries wired in parallel for charging purposes, headlights, and such, and connected in series for starting by energizing the solenoid. I worked for a few months between college semesters on the assembly line at the same battery factory that sold the 8V batteries Dad developed the adapter kit for. Every few weeks we would make a limited run of the 6-12 batteries.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!