Yes, all of that is correct . . . however, that isn't what he puzzle truck is. Ward Thorne, of Chicago, Illinois, started the Thorne Motor Corporation in 1929 to build delivery vans using the gasoline-electric propulsion system that he ultimately patented in March 1933. The gasoline-electric drive system quite simply in-stalled a Continental four-cylinder engine in the conventional location, but attached a generator to the back of the engine instead of a flywheel and transmission. The generator, which put out a maximum of 1,000 amps at 80 volts, then powered an electric motor located just ahead of a conventional rear axle.
Using this gasoline-electric drive system, a delivery man still needed to rev the gasoline engine to produce electricity for the motor--the generator directly powered the motor, not a bank of batteries between the two--but he only needed to set the parking brake and allow the delivery truck to idle as he made his stop. Once ready to go again, he only had to release the parking brake and step on the accelerator. No clutching necessary, and because the electric motor makes all of its torque right off the line, the gasoline engine did not have to rev as much as the engine in a conventional drivetrain, thus it used less fuel than a conventional drivetrain. By 1932, Thorne fell into debt to Hertner Electric of Cleveland, the company that supplied the generators, and to settle the debt, Hertner bought Thorne and moved the company to Cleveland, where Thorne built trucks through 1937. As Thorne went out of business, its chief electrical engineer, Bernard Flory, went back to Chicago and approached Walker about using the Thorne's basic engine-generator design instead of the oft-problematic batteries that powered the Walker motor-axle. So Flory found himself a new job and Walker began building the Dynamotive line of delivery trucks just as Flory suggested in 1938, continuing through 1942, when the company switched over to war production. Walker remained in business after World War II, but did not continue delivery truck production.
The truck in the puzzle is a 1936 Thorne, built before the later Walker collaboration.