I have several ebay and/or craigslist picture-sets of the early 1960's Raleigh Gran Sport, with "High-Tensile" steel tubing and indeed, it has wrapover stays.
I should say, however, that this may not be an especially lightweight frame. Although I've never owned one, the wrapover bikes used a standard one-piece casting for the wrapover part, because weight didn't matter and it was faster that way. Such Frame/Fork combinations generally weighed about 8 lbs (vs. 6.25 lbs for a reynolds 531 frameset.)
So if this bike has an 8-lbs frame, it would be more or less equivalent to a 1970's Raleigh Grand Prix. The all-chrome carlton cobra was similar.
- Don Gillies
San Diego, CA, USA