Ford numbered its trucks and Broncos with an eleven-character serial — truck line, body series, engine, plant, year and a serial from 10001 — until the 17-character VIN of 1981 with the 1FM (multipurpose vehicle) and 1FT (truck) identifiers; the 4x4 is read from the body series (F11, F26, F36) or the model code. The M151 carries a data-plate serial and an Army registration, not a VIN.