That is an
'84 High Sierra, the combination of the decals, braze-ons and fork were unique that year. Here is another example that recently sold on eBay:
http://www.ebay.com/itm/200899501203
Note that Schwinn built frames and acquired other components often months in advance of production, so it would be normal to find '83 dated frames and other components on '84 model year bikes.
Your headbadge is probably original since it is riveted on and date stamped, but if so that is nothing more than either a mistake or the factory simply ran out of the proper "High Sierra" labeled badges on the day that bike was assembled. Replacement badges could be ordered from a dealer back then, but they would be unstamped. The assembly date was normally stamped on the badge as a 4-digit number with the first three digits indicating the ordinal day and the last digit indicating the year. My guess is that the last digit either didn't make it or was obscured by the rivet, in which case your bike was probably built on the
122nd day of '84.
The ground-off serial number unfortunately indicates that the bike was likely stolen at some point in the past.