The presence of dual bottle bosses, a pump peg and cables running under the BB shell, in conjunction with a integral but not unicrown fork crown, suggests late 1980s. There doesn't appear to be a front derailleur tab and it lacks embossing which would suggest no better than mid-range and rule out a major brand. Chrome stays but a painted fork are contradictory, so it may be replacement fork and a repainted frame. It's probably Japanese or Taiwanese. The serial number may allow us to determine the exact year and/or manufacturer.