Based on the 26.8mm seat tube, 1984 Z-series components and 27" wheels, the most likely candidate is an upper entry level, Japanese or Taiwan manufactured frame. Consequently, the main tubes are most likely a manganese alloy, though CrMo is also possible. Six speed would be correct.

Based on the serial number format, it should not be a Nishiki. A Raleigh would also appear to be unlikely, as their prime Asian supplier was Merida, who used a different format.

However, the format does match a late 1985 Miyata frame. The components would indicate a model 110, however there are numerous variations to specs. It did not have a pump peg or shifter bosses. It did have bottle bosses, which you do not mention. The binder bolt ear and crown style do not match. Being a late 1985 frame, we should not rule out the possibility of a 1986 model, but there are still too many variations, namely the pump peg, binder bolt ears and crown style. So it would not appear to be a Miyata despite the serial number format. I have gone though this somewhat lengthy analysis in the event that somebody picked up on the serial number fomat and suggested a Miyata.

However, assuming Miyata manufacturing , the other possibilty is Univega. This would expalin the serial number format, while allowing for detail differences. Components and era would suggest a Maxima Sport. Unfortunately, while I have components specs for this model. I do not have any visual references to determine if the frame details match. Hopefully some other forum members will be able to confirm or disprove this.

The last possibility is that there were other manufacturers using similar serial number formats.