The OP's ATB definitely pre-dates the 1989 catalogue, as SunTour XC 7000 Accushift was only manufactured for the 1987-1988 models years. It was SunTour's mid-range ATB group,below XC 9000 There weren't many manufacturers specifying it but some 1987 competitors featuring it included the Zebra Fresno ($500 US), Nishiki Ariel ($550 US), Kuwahara Cougar ($559 US) and Miyata Terra Runner. These models were typically 2nd or 3rd in their respective ATB lines, competing against bicycles equipped with Shimano Deore (not Deore XT but the mid-range group later called Deore DX).
The Osaka reference in the catalogue implies Japanese manufacture. Unfortunately, Osaka was a major bicycle manufacturing centre of Japan. I once compiled a list of about twenty bicycle manufacturers and bicycle trading companies located in Osaka. Undoubtedly, there were even more and if the Osaka reference is to a trading company, there's still a possibility of Taiwanese manufacture, though by 1987 trading companies played a much smaller role than they did during the early 1970s bicycle boom.