Without shifter braze-ons, I'd guess that the frame is late seventies, early eighties. It's possible that the headbadge is not original, though unlikely.

If you have any doubts about the quality of the frame, just strip it and weigh the frame and fork with only the pressed-on races for the headset in place. If you're at or near six and a quarter pounds (2.8 kg), it's almost certainly a double-butted Reynolds 531 or Raleigh 555 tubeset. Another clue is seatpost diameter: anything over 26.6 does not equal 2030 tubing.

And decent components too. Hey, for $50, ride it like it's a Carlton!