O.K. I was wrong about the plate. Here is the real decoding. The letter E in the upperleft corner is the county. E in 1930 is Yavapai county. Yavapai county was assigned a block of numbers. In 1930 their block was 120,000 to 130,000. This plate is 122,758. Why they separated the numbers by hyphens like that I don't know.