djm - The hood and fenders were the give away. I checked the production records I have copies of, and all 1957 Super 55s have the fuel tank cap sticking up out of the hood. I was thinking it was February of 57 that they started the new hood, but it was from the start of the year. They will also have the word OLIVER embossed into the rear fenders.

Laharview - Definitely not a 1957. It is actually an early 1955 model.