Those rollers are used for friction winches, a rope is wrapped around the roller several times, by pulling on the rope it grabs onto the roller like a friction clutch and transmits the power from the winch, easy way to control operation and loads of pulling power, the tighter you pull the rope the more power transmitted, let up on the rope and the pulling stops. The belt drive mentioned by PTO would not have had sides on the pulley; the pulley would be slightly crowned in the center but no sides or flanges.

The spectators seem to be dangerously close to the action. In particular, the lone guy on the right seems vulnerable. I see no chains to safely hold this vehicle should it slip backwards, so why would one assume that it would fall back in a straight line?

Notice the wooden box o' rocks and other stuff, including a shovel, behind the cab temporarily (judging by its cobbled-together look) mounted as far forward as possible in an effort to get some extra weight on those front driving wheels OR to minimize the possibility of a crowd-pleasing 1928 FWD truck wheelie. I wonder what water tower that is in the distance?

One final thing, whatever the photographer was standing on, it's much higher than the far side of the draw/arroyo/small canyon. His position so near the action and unobscured view seem to indicate he was shooting from a building that stood on the edge on the high ground. This could have been at the Army's Aberdeen Proving Grounds in Maryland, not far from me, which has been testing military equipment including tanks and trucks since 1917. Note the uniformed gent in the foreground. At first I thought that was a boy with the bike, suggesting some informal setting open to anybody, but I think he's an adult, so it could be on government property.

A stretch of Rock Creek Parkway between M and P Streets (before the bike path was paved).

Interesting that the kids and the one on the bike got in front of the suits and the Army officer observing the demo!

Whether he makes it to the top depends a lot on how fast he was going when he started the climb.

It might be possible to figure out where this photo was taken if anyone recognizes the water tower[?] in the background above the truck. It looks like there may be a sign painted on it, but I can't make it out.

Wonder what the wicked looking winch on the back was to be used for. Pretty serious towing or dragging by the look of it. Note the rear towing hooks on the frame as well.

FWD/Seagrave is still alive and well in Clintonville, Wisconsin, where the High School team is the “Truckers.”

Subtitled "Accident waiting to happen."

It looks like those rollers would be engaged against the rear wheels, in turn operating the exposed gears. To lift a dump bed, perhaps?