Were built years 1956 and 57, need tractor SN to verify, 1956 started 400001, 1957 405671, Engine sn not used to determine year. Tractor is not MF, is a Ferguson 40, tinwork should be cream color instead of red. Massey-Harris sold same tractor as model 50 with tinwork change. MF 50 started in 1958 as bcp mentioned, MH and Ferguson merged in 1953, MHF was used on some SN tags long before name was changed on hood. Early diesel 35 used Standard Motors 23C engine, MF bought Perkins in 1959 and started using Perkins diesels instead of Standard or Continental like MH used before 1959.