Here's one T-Mar to throw a wrench into the works, but will add it to the data-base anyway. Going by the Shimano 600 date codes the components were made in April '85, so that helps in narrowing it down a bit.

Centurian 'Elite RS'

frame: 'Tange 2' double-butted Cro-Moly seamless tubing (serial # KF51074)
fork: 'Tange' cr-mo steel fork blades.
headset: 'Tange' falcon
bars: Nitto 'Olympiade 115'
stem: Nitto 'Technomic'
calipers: 'Diacomp' Royal S' sidepulls
levers: Diacomp Gran Comp' that are drilled
crank: Sugino ALP with 52/42 Sugino chainrings
pedals: Shimano '600' toe-clip and strap
derailleurs: Shimano '600'
hubs: Suxue 'Sealed-Tech
wheels: 'Araya' 700c 36-spoke steel rims
seatpost: 'Sugino' SP-KC fluted