Really cool piece! I don't believe it's a Hercules, the emblem on the tank does not look like any I have seen. I'm actually thinking it is a carnival ride sort of build-up:
Sachs 4 speed engine, top of the line moped, entry level motorcycle power plant (mid to late 1950s is my guess), I would not be surprised if it were empty
Wheels rims look similar to push bike or very early bicycle, not much strength for riding, front hub is from a bicycle
Neither wheel appears to have a brake, if the rear does then it is tiny
The muffler was painted red (no chrome)
The rear shocks appear to be cast aluminum or chromed steel mock ups, probably with a spring inside. No front suspension
There appears to be no gas filler cap or petcocks on the tank
Frame appears to be cast or forged h-beam construction or possibly crushed tube
The front wheel attachment is by flattening the end of the fork tube and cutting a slot in the bottom of it, not very secure for an engine driven machine
No sign of or remains of any cables or wiring harness
The running boards are huge (to keep little feet safe), stick out quite a ways with a skid underneath, would not take much of a turn to hit ground. The skids under the running boards are where the arm of the ride mechanism attached.
What should be the drive shaft appears to have bolts through it holding it in place
No sign of there ever being an emblem on the left hand side of the tank, only had to look cool on the outboard side
If I had it I would make it into a ridable motorcycle and ride the heck out of it