A steel mystery koga miyata skyrunner?

[RetroDavy]

Based on info in the link below, if the serial number starts QB it's likely a January 1988 frame, which supports LeonL's suggestion that it's a later colour scheme on the previous year frame.

I don't know if the other numbers denote a model. I haven't seen anywhere that they might but someone else will know better.

I should be getting a late 1980s Koga Miyata Ridgerunner frame myself so will report back when I get the serial number.

Asian Serial Number Guide - Bike Forums

Classic & Vintage - Asian Serial Number Guide - Many of you will be aware of my penchant for collecting and analyzing serial numbers. This guide compiles the results of a decade of data collection of pre-1990 Asian serial numbers. The guide is not necessarily comprehensive, as it only represents...

www.bikeforums.net

 

[Elev12k]

Judging by all the details this look like a 1988 ValleyRunner to me.
TerraRunner: nicer lugs
RidgeRunner: nicer lugs, brazed crown forks

 

[RetroDavy]

Reporting back -

My 1986 Ridge Runner frame was likely made in November 1985, going by the database linked in the post above. The paint is the same as in the catalogue but the frame doesn't have bottle bosses under the down tube, and it's got a rear u brake whereas the catalogue shows cantilevers. Though these seem like the sort of changes that often happen between catalogue photos being taken and model details being finalised.

Thread with photos here: https://www.retrobike.co.uk/threads/koga-miyata-ridge-runner-1986.453796/#post-3325579