I see the same serial number on both fork steerer and left dropout. That is a common pattern (used by Carlton and others) so while it may exclude some makes, it won't lead to a speedy identification. The same hours for the lugs, which are very nice but not very rare.
The lack of a derailleur hanger points to early fifties, I think.
The two serials match, so at least he knows the frame and fork are an original pair. I agree with a 50's date.