It looks more chain-case than chain guard to me too. The chain guard on my 1967 Raleigh RSW is a much more flimsy-looking thing. Agree also that the frame looks a bit earlier, even just from that vague shot!
Confession time. The frame in the photo is not actually my frame it's a picture I found which has the same mounting hole as my frame.
My frame is this one. 25" seat tube, 126mm rear dropout spacing.
Currently prepping for a respray.
There are some other mounts, one on the inside of the non-drive side seat-stay (dynamo mount?); also 2 small clips brazed onto the underside of the down tube. One close to where the down-tube shifters would be and one down closer to the bottom bracket. Not sure what these do exactly.