1937 Ford 1/2 ton VIN?

[64cyklone]

Hello! First time to Forum. I have a '37 Ford pickup and the frame VIN (I know, there were no "VIN's"), or "serial number" begins with a 20- 304////. I thought the "78" Series, or Model trucks began with an "18", as my first '37 did. This number is not on the title (20), but it is validated finally and legal to run. Do anyone know what the "20" number designates? Thanks! Bill (64cyklone)