First look over the right side frame rail good, especially in the area of the steering axle rear spring hanger..
The first 3 digits will be the model number then production number starting with the first of that model thru the whole production run.. With that number I may be able to help you place a year on it??
Another contact would be David Kellerman in Sparrow Bush NY Email me at email@example.com
and I can give you his contact info..
Diamond T and Brockway Collector