Originally Posted by
T-Mar
A 25.4mm set post is indicative of hi-tensile steel. This, in combination with a forged rear dropout with an integral hanger and the complete absence of braze-ons, other than cable tunnels on top of the BB shell and some cut off cable stops, has me leaning towards early 1980s (I'm wondering if the lead 9 indicates 1979 manufacture). I also believe it is Asian in origin, based on the rear dropout style. Given the OP"s location, it is probably some SE Asian brand that was never marketed in North America.
Thank you for the detailed insight! It really helped. For the moment, I’ll just sand and paint it in plain color just to avoid any more rust while I seek for its origin. Thank you again! 😃