The subject bicycle has been substantially rebuilt. The relevant frame features are the stamped drive side dropout that requires a claw style rear derailleur and the presence of top tube cable stops. This tells you that it is not a CrMo frame. Consequently, it would be one of the 1024 frames, which was a hi-tensile steel alloy. Miyata did offer frames with this alloy in plain gauge, single butted and double butted versions."Light" is a relative term but few members would likely use it to describe this frame. Even the double butted 1024 tubeset was about 660g heavier than the CrMo double butted tubeset used on the better models of the era.