As stated earlier the serial number is the format of Miki Sakai. Miki was mostly a bicycle frame manufacturing company. Miki was contracted by dozens of bicycle brand names large and small in Asia, Australia, Europe, and North America.

The fork is the unique part of this frame set. I have not seen a Miki Champion No2 frame with this style of fork.

A clue to which brand name contracted this bicycle may be your geographic location.