This is interesting and has seemingly conflicting characteristics. The name and decal style are typical of a chain store brand but there are indcators pointing towards something better. It has decent but not overly agressive geometry. It has recessed brake nuts, bottle and shifter bosses, a pump peg and cable routing under the bottom bracket, yet the forged dropouts still have eyelets. This combined with the spacing points towards a lower mid-range, mid-1980s model, yet it doesn't have the tubing decal you'd expect on this level and era.
Regarding the components, the derailleurs and frewheel are almost certainly a later, indexing upgrade. The component most likely to be original is the headest and it is Shimano unit. That scalloped style was introduced in 1978 and used though 1987 on the various 105, 600 and Dura-Ace groups. Assuming it is OEM and taking the other characteristics into account, a 1983-1986 Shimano 105 headset is the best candidate.
The best indicator to the frame level is the seat post diameter, provided it's not undersized (i.e. the cinch slot is nor noticably pinched). The serial number may provide a clue as to the year and origin. Other clues may be provided by the dropout brand and bottom bracket threading which should be stamped on the cups.