The position of those eyelets on the rear stamped dropouts might be a clue--seems unusual. The "hearts" are stops for gear cable clamps and are fairly common. A good clue would be the threading of the bottom bracket. The cup design looks like Universal Japanese (or Taiwanese) Bicycle to me, so my guess is a mid 80s, relatively low-end Miyata/Fuji/Panasonic/Shogun/Univega.

Neal