RPO codes => nothing stands out like ZR6 for a car prepped for a national car show event or notes for law enforcement turbo regals.
Your VIN is one of the interesting few having the last six of beginning with a 2. There were some '86 turbo regals made in the Fall of '85 that came that way. My records have most from month of October. your cowl tag shows production week. top left corner might show G 10 then letters A or B or C or D or E.
From build records and VIN sequence, I'd say your car was built the 4th week of October 1985 (showing G 10 D). I know of a few '86 T-types / GNs having VIN sequence within a few #'s of yours.
G = Model Year =1986, H=1987
10 = Month; 12 months in a year
A = first week of the month, B=2nd week, C=3rd week, D=4th week , E=5th week
Buick division vehicles typically have last six of VIN (production sequence) beginning with a 4. Just as Chevy is division 1. Also reference 3rd digit of VIN which denotes witch GM division. GM division 2 is Pontiac. GM division 1 is Chevy. GM division 4 is Buick. And 3 = Olds; 6 = Cadillac; while 7 = GM Canada(for Canada built vehicles). All turbo regals were built in the USA then exported to Canada. Heater core emissions label would show that export wording.