My reference point is with 1960's frejus frames. I ones that I have all have the serial number stamped on the seat tube. The bottom bracket is solid, not drilled and usually has the frame size marked (i.e. 58, 60, ect). With frejus frames, I look for the oiler ports on the head tube and bottom bracket along along with slots at the top of the seat post. Granted, my bikes are older - but I don't see any of these features in the OPs pictures. Granted, things may have changed in the 70's - but my (uneducated) guess is that it's just decaled as a frejus. The drilled bottom bracket shell is out of place. However, it's still a very pretty bike -