Yup – the PO’s were made from 1937 to 1950, with only military versions being made during WW2. They are 22 HP and have no water pump impeller, so if you idle too long, they overheat. From 1941 to 1950, they were all model PO-15. Your gas/oil mix is 8 to 1.
Here is my PO-15, except I have since replaced the oak stick with the proper tiller handle:
