KAN = Kansas City, MO
The number following the build date is the batch or sequence number, it is also found on the build sheet. (0501 on the attached trim tag, 8711 on yours).
Since you didn't list the Group numbers for the option codes, they can't be determined without a picture of the trim tag, but the most common are shown below.
Assuming Group 1:
E = Tinted glass (all windows)
Assuming Group 2:
C = Custom padded seat cushions
Assuming Group 3:
C = Padded dash
Assuming Group 4:
C = exterior belt reveal molding
Buickman Award 2015
1957 Special 4-door Riviera (hardtop) model 43