+1, given the serial number and location, it sounds like it may be a Giant manufactured frame. As suggested, check the other dropout.

Toyoda would have been the importer/distributor. I'm not sure exactly what the business relationship was, but Toyoda were also the Miyata distributor/importer until about 1982/1983. At that time, Miyata Industries became the listed importer but the address did not change. I'm not sure if Miyata bought Toyoda, just the facilities or if there had been corporate ties all along.

Personally, I wouldn't put too much weight on the resemblance to Nishiki. It was not uncommon for lesser brands to mimic the cosmetics of more more popular brands. Regardless, the Nishiki brand was owned and imported by West Coast Cycle Supply, so the Toyoda reference would end the possibility of their being related, even if it turns out to be a Giant frame. At the time, Giant was a Taiwanese contract manufacturer who manufactured bicycles for numerous other companies.