I still think it's got to be something other than a Raleigh/Carlton. There were many British builders who used the curved brake bridge, and for many years, so that's not a good clue. And the serial number means zip to me, except it's short which points toward a smaller shop (smaller than Raleigh). I thought of Ron Kitchings since his business was active in Harrogate, Yorks (not Newcastle but SORT of nearby) for decades, from the 50s thru the 90s...but most of the frames built for his trade would have Zeus or Suntour dropouts, and I don't know about Nervex being a lug he imported, typically his trade was in Milremo (his rebadged BCMs) or Prugnat. Harrogate also was home of builders Metcalf and Mason, who teamed up with Kitchings to be MKM...more possibilities from Northern England Builders include such worthies as: Priory, Tower, Whitehead, Mal Rees, Heatons, Lakeland, JRJ ( Bob Jackson), Woodrup, Merlin, Harry Quinn, Harrison, Harry Hall, Denton, Harris, Jack Taylor, AE Butterworth, Henry Holmes, Ellis Briggs, Mercian...take your pick! One thing I've read about early Carltons is that all their serial numbers have a letter code such as J4364, or S2568, since you don't have a letter...it's not Carlton.