I am not a huge expert so maybe only count my input at 1/3 of the above: But, I concur (as if they needed it) that tange champion
#2 is a very good bet just due to the japanese drop outs and the seatpost size which coorespond, and the chrome, which puts it in teh range of a semi-pro which was champion
#2 . But without a Serial# it seems like it must not be a major player and probably a small builder.
and if it were a small outfit, it could be any combination of tubing: like my zunow does not have a tubing sticker because Kageyama liked to pick a tube that worked best for the bike and maybe the top is champion 2 while the down is champion 1, seat tube.... who knows? -and he even had them make custom tubing just for him so it has no standard number
So what I am saying is: you may just have to wonder: I think you are probably safe in that its Tange, but other than that... there is no way to know without using an MRI or something.