That special GB stem with the elevated perch for the bolt head - I have also seen that on an all-original 1971 professional (or international) and its a very early part. You could always check the serial number on the bottom bracket it probably say "Gnnnnn" which indicates 1972 (Fnnnnn = 1971, Ennnn = 1970, I'm guess Dnnnn = 1969). Also the saddle has a datemark on the cantle plate, and most weinmann brakesets have a datemark on the back of the bridge, check
Vintage Trek Bikes- Information on Steel Road Bicycles made by the Trek Bicycle Corporation, bike for how to decode the date mark(s). All the drivetrain parts (except bars and stem) are replacements. Not surprising because your bike came with a simplex gear system, originally, and everything eventually snaps off in a simplex gear system.
I own a 1968 (anniversary badge) competition with the heron/flame head badge, and that one has a nervex BB shell, davis crown, and campagnolo dropouts, and the weird flat rear centerpull bridge made not from a semicircular tube but from a trapezoidal piece of flat metal. I believe the next year they might have used zeus dropouts. Anyway, the flat metal non-semicircular brake bridge makes your bike pre-1970.
As I said, I have this exact same frameset except with campagnolo dropouts. It was the ugliest raleigh ever (choose between stovepipe black or icky british racing green), so asap most people repainted it. My frameset cost $100 at a Los Angeles thrift shop a decade ago. Mine, I took off the braze-ons and repainted it as an RRA (1973).