I guess it could be a Korean copy, mine is stamped though do maybe not. My understanding is that not all the Nagasawa have such ornate details. The ones made for local racers were far less decorated and more functional.
I don't know about Nagasawa frames, but the track ends on your frame look like Suntour ones, which means it could be from the 80's, and might explain why it is not as ornate as current ones.
I guess it could be a Korean copy, mine is stamped though do maybe not. My understanding is that not all the Nagasawa have such ornate details. The ones made for local racers were far less decorated and more functional.
Who knows?