Nishiki's most common tubing supplier was Tange, however they also used Toshiba (entry level) and Columbus (high end). The two other high end models, the Maxima and Cervino, used Columbus SL and bore the appropriate decals. However, the big clue is the seat post diameter. If it uses a 26.8mm post, it is likely Tange #1. If it uses a 27.2mm post it could be Tange Prestige or a Columbus tubeset, but I believe the Ultimate is too old for the Prestige tubeset. A Columbus tubeset will be evident by six helical ridges inside the bottom of the fork's steering tube.

Ishiwata and Reynolds tubesets are also outside possibilities, but based on historical usage, Tange and Columbus are the most likely candidates.