Hi T-Mar,
Just wanted to add my Centurion to your database. It doesn't match the majority of your numbers, but does match the "1984 exception". The serial number is 4G13748, and it's a 1984 Pro Tour 15.
Some details that have been discussed by some others (Wildwood, alanbikehouston):
-It's the brass/bronze/champagne color which they call "Taupe".
-The wheels are 27".
-Internal wiring.
-I believe that the frame actually was entirely chromed: I've got a lot of miles on mine (and therefore quite a few scratches...) and there's chrome underneath all of them... including on the head tube.
-It came with LeTech (SunTour) front and rear derailleurs.
-Mine matches (matched... there are some changes now) all the specs that alanbikehouston listed except the brake levers are DiaCompe (GranCompe?), not Shimano, and the stem was an SR. The levers are drilled, though.
As A.Winthrop mentions, there's a catalog that includes this bike at Sheldon Brown's site:
http://www.sheldonbrown.com/centurion1984/index.html
Ooops, just found this template from A.Winthrop (though I'd add a "Made in" field if known):
GENERAL DESCRIPTION:
Centurion ProTour 15 1984
Color : Taupe (w/contrasting head tube)
Weight : ?? It's a touring bike... never occurred to me to weigh it
Serial Number : 4G13748
Made in : Japan (says the sticker)
COMPONENTS:
Frame : Tange Champion #2
Fork : Tange Champion (with low rider bosses)
Bars\Stem : SR Custopm/SR ARX
Brakes\Brake levers: DiaCompe Gran Compe cantilevers and DiaCompe levers
Rear derailleur : SunTour LeTech
Front derailleur : Suntour LeTech
Downtube shifters : SunTour Symmetric (trims the front when you shift the rear)
Crankset : Sugino AT (marked C-9 175) with 28-42-50
Bottom bracket : [Don't remember]
Freewheel : SunTour Winner 5-spd 13-28
Chain : [Don't remember; spec sheet says black and chrome DID]
Hubs\QR : Suzue Competition 36F/40R
Pedals : [Don't remember; spec sheet says SR SP100]
Saddle : Vetta
Seatpost : SR Laprade
Rims\Tire size : 27" rims 27 x 1-1/4 tires
Just FYI, I've done a lot of touring on this bike, and I made some changes here and there (sacrilege!):
Hubs: Phil Wood.
BB: Phil Wood
Pedals: SunTour Superbe Pro
Shifters: SunTour bar-con
R. Derailleur: SunTour XCD
Freewheel: SunTour Winner Pro 6spd (oh man, does this mean I need to get a new paint job that says Pro Tour 18???)
It's a beauty and is still going strong.
Thanks for everyone's work on this!