A quick glance and I thought they were Haden "bird's mouth" lugs; but no. At least not the same as on my '72 Raleigh Pro. Possibly a lower grade copy of them. Definitely a little rough in the quality of the workmanship.
Thanks Midlife, you have noted my preferences! I edited the photos as the head tube has an unusual badge, which I am attaching, which gives away the manufacturer. It is a metal badge, which suggests it is at least pre 1978 / pre Elswick Hopper takeover, when they seem to have switched to the adhesive type.
Any ideas about the badge? It clearly is a "real" Falcon as it has the familiar Falcon typeface and the bird is very similar to that used on the classic metal Falcon badge used until about 1978. It also says "made in Birmingham" and Falcon cycles moved to Barton-on-Humber from Birmingham in 1968. Would that make it a 1950s/60s frame?
I have no evidence that in this era Falcon were outsourcing frames from the far east.
There are plenty of Falcons of that era about still but this is only the second time I have seen this badge, once for sale on its own and now recently sold on a frame. I have a database of photos of almost a thousand Falcons and it has never turned up on any of those until now.
If anyone has any knowledge about this badge I would be very appreciative.
On looking at my database, the same lugs are used on most of the 1970s Black Diamonds. Those were very prolific in numbers and were a non-531 tubing frame. This frame had been resprayed and the rivets you can see in the photo, I guess would have been put in after that. So, it might not be its original badge.
I am not sure what you mean by the olympic rings era. They were used as early as 1956/57 as per the attached photo. I have this badge on a very early Club Special Falcon. Note how the manufacturer is shown as "RCI Ltd". Robert Cycle Industries were bought out by Coventry Eagle in 1958, so the rings were used presumably from the beginning in 1956.