I think you're all right about it being a Grand Prix...then 20/30 high carbon steel for sure.. I know in 1968 Carlton hand made bikes for Raleigh - but I don't know what year this is. Anyone know how I can find out the year using serial #? It' great that we've narrowed it down to being grand prix though... was grand prix mid-level for it's time... "close coupled geometry to give an exceptionally lively and responsive ride" is what one 70"s ad claimed!