Stays of this type have been attributed to the framebuilder Tom Board. I have a 1967 Geoffrey Butler built by Cliff Shrubb with this type of stay, unlike the"shot-in"type sometimes used by the SBDU.
SBDU founded in 1974 at Ilkeston, and Carlton bought by Raleigh at the suggestion of a certain Mr Reg Harris.
Nice machine although a few hands too tall for me!
Co-founder of a V-CC section, member South Eastern Road Club and owner of - 2005 Bianchi Reparto Corse (modern), 1985 Raleigh SBDU Pro Super, 1984 Raleigh LU Corsa, 1980 Allin Stan Butler Special, 1978 Ron Cooper, 1975 Bill Philbrook tourer, 2 x very early Roberts (mid/late 1960s), 1966 Raleigh Superbe Roadster, 1964 Allin Stan Butler Special Belgique, 1951 Hobbs of Barbican S/C, 1950 Hobbs of Barbican S/C, 1947 Hetchins Super Special, 1908 Centaur Featherweight. 1988 Specialized Stumpjumper.