Winchester Model 101 History   Back Winchester Model 101 Serialization 12 Gauge Serial Number Range Year of Manufacture 50,000 - 50,499 1959 50,500 - 51,999 1960 52,000 - 52,499 1961 52,500 - 55,999 1962 56,000 - 63,499 1963 63,500 - 75,499 1964 75,500 - 91,499 1965 91,500 - 102,999 1966 103,000 - 110,499 1967 110,500 - 117,999 1968 118,000 - 129,499 1969 129,500 - 140,499 1970 140,500 and Up 1971 The Winchester Model 101 12 gauge was manufactured after 1971, but no serialization records currently exist. 20 Gauge, 28 Gauge, & .410 Bore Serial Number Range Year of Manufacture 200,000 - 208,999 1966 209,000 - 210,999 1967 211,000 - 214,999 1968 215.000 - 220,499 1969 220,500 - 228,499 1970 228,500 and Up 1971 The Winchester Model 101 20, 28 gauge and the .410 bore were manufactured after 1971, but no serialization records currently exist. Note: The 28 gauge and .410 bore were first introduced in 1968.