This was a confusing name, just as Broken mentioned there was a bike company called Centurion BUT Nishiki also made a bike called the Nishiki Centurion, so check to see which it is. The Centurion road bikes was made by Western States Imports who also made DiamondBack which was their BMX and MTB line. The Centurion name was started in the early 80's and only lasted about 10 to 15 years because road bike sales fell off and MTB sale shot through the roof so Diamondback became the hot selling bike brand.

If it's a Nishiki that was a excellent bike in it's time and should be either Tange Prestige or Ishiwata 019 tubing either is an excellent tube set; just ask the seller which tube set (this of course would also apply with the Centurion in regards to the tubeset).