Originally Posted by T-Mar

Thank-you for posting. The Giant s/n format didn't change in the early 1990s. That's late enough in the calendar year that I would suspect a 1991 model. Regardless, it's easy enough to distinguish between the two model years based on the frame features. The 1990 model still had the derailleur cables running along the down tube, while the 1991 model had them running along the top tube. There were two versions of the Impact in 1990, an MOS version ( SunTour XCM/XCT, $350 US MSRP) and a Pro MOS version (Shimsno 300 LX, $399 US MSRP). In 1991, only the Pro MOS version was offered, though the MSRP had increased to $425 US. Enjoy your new acquisition.