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They don't give you much. It says it's an F1 or half-ton
R is for the flathead V8
1 is for 1951
HM is for Highland Park, Michigan assembly plant
27736 is the serial number string
I use a book by Cars & Parts Magazine called "Catalog of Ford Truck ID Numbers 1946-1972" I found it on ebay several years back and it's correct for most things.