Badge worn by Japanese built Schwinns such as the pictured 1980 Schwinn Traveler. 

Beginning around '73/'74 some Japanese built Schwinns began sporting headbadges with a 4-digit stamping that represented the assembly date and consisted of the ordinal day of the year and the last digit of the year (2456 decodes to the 245th day of 1976 or 1986 -- use decals and components to determine the decade). The ordinal dating was adopted for Schwinn's domestic production in 1976.  The date decoded from the serial number of the frame can vary from the assembly date by quite a bit.

In the 1980's a number of different Schwinn bikes had the model name on the headbadge. Here is a Tempo example.