What is the date of manufacture of a Stevens model 94 series M single shot 20 gauge serial number B820164?

The Stevens Model 94 series M single shot shotgun was manufactured between the late 1940s and early 1980s. The serial number B820164 suggests it was likely produced in the 1960s or 1970s. However, for an exact date of manufacture, you would need to consult a detailed reference guide or contact a firearms expert or the manufacturer directly, as Stevens did not maintain detailed records for these models.