Kuwahara dating
Hi. I've owned over 15 Kuwahara mtbs over the years, and there is precious little on them available except German-market models of the early nineties (which differ markedly from Canadian market models of the same era).
Your Savage is likely from 1990. For the 1989 model year Kuwahara started putting it's brand name on the top-tube (1988 and earlier was on the down-tube). However the 1989 Savage was an 18 speed, and had a different model decal. Unless I'm mistaken, your Savage is a 21 speed, equipped with Shimano's 300gs group set, with ST-M020 push-push trigger shifters.
The best way to date your bike is from looking at the Shimano date codes on the various components. I wouldn't be surprised if in doing so you saw a lot of late N or early O date codes.