Hi Mind 527. Your frame is definitely steel, either Hi tensile or possibly Ti (Tube Investments Ltd, not Titanium!) 'Tru-Wel 205'. Carlton used a lot of Tru-Wel 205 for their mid-range frames, as did Falcon and Elswick-Hopper. The foil decal fits in very well with the early 1970's vintage. I can remember these bikes hanging in the windows of my four LBS's in about 1972-3. Tru-Wel is not as light as butted 531, but by this time Ti owned Reynolds, so the tubing was most likely drawn by the same men in the same factory in Birmingham, England. OK it's not the top-end frame but it will make a nice ride and if you're building it into a fixie it will be perfect, provided that it fits you. This may even be rarer, since they were comparatively cheap people did not consider them particularly valuable and scrapped them when the components wore out - so less surviving examples. Please don't chop off any brazed fittings though, that would destroy the future value of this frame.