Originally Posted by A.Winthrop

Hi Nemo,
.
Have another look at the '84 Centurion catalog on Sheldon's
site. Among the scans you will find a LeMans 12, which looks
just like yours to me... even the same blue\silver head tube
colors and scheme. The Sugino cranks look the same as yours
as do the Suntour downtube shifters.
.
There is also among the scans a specs sheet with detailed
specs of all the offerings for that year, including the
LeMans 12. You can compare those with yours to help confirm
your bike's ID.
.