Nice find. Love the barn finds. The serial would be stamped on the right side. Early front axle and collared spindles. No creeper hole. Blue air cleaner was probably a PO repaint or from something else. What was the engine serial number. If it was a prototype, the engine may have a prototype serial number unless it was replaced.
Duke,
Correct me if I'm wrong but didn't the production O's have footrests with holes stamped in them? Paul Bell owned a prototype, serial number 409 and the foot rests were smooth. They changed them to stamped holes to improve traction when your feet were wet. Foot slippage would hurt, especially with the shifter where it is, OUCH!
I think Timmy DeLooza owns the prototype now. I'm not too familiar with early O's serials 501 to four digits. It would be very interesting to see the serial number of this one.