FWIW, the serial number format is consistent with Nomura of Japan and in conjunction with frame features would indicate early 1984 manufacture. They built frames for numerous brands, including Centurion, Niko, Novara, Raleigh and Shogun. The 26.6 seat post is consistent with many Tange tubesets. Based on the way the stays are exiting the BB shell, I'm assuming this is an ATB frame? It looks like an early Diamond Back model., though it would be hard to say which one, due to the absence of OEM parts.

Edit: In 1984, according to member frantik, that year's catalog had 3 ATB models, the Mean Streak, Trail Streak and Sand Streak. My database has serial number samples for two 1984 Trail Streaks that indicate manufacture by Fairly of Taiwan and they used lugless construction. Consequently, the subject bicycle, having been manufactured in Japan, with lugged construction, should be the top Mean Streak model. If you look closely, the dropout flats are chromed on the attached Mean Streak photo. Tubing decals on extant Mean Streak indicate Tange Champion Mountain Bike, plain gauge, CrMo.