The actual model name is circumspect given that Nishiki were spec'd differently for each market and the OP is located in the Philippines. However, it does appear to be a high end model given the tangs on the inside of the fork blades. Other frame features suggest origins in the ONP, whose frame was eventually employed on other USA Nishiki models such as the Professional, Ultimate and Superbe. My overall impression is very late 1970s to very early 1980s. It is likely Tange Champion #1. As noted, the serial number will at least allow us to narrow down the original market and year.
As an example of market variance with Nishiki, attached is the catalogue entry for a Canadian market, Nishiki Superbe. It has top tube cable tunnels braze-ons, unlike similar USA market models of the era. Frame features, including braze-on allocation, are a close match for the OP's prospective purchase.
