Apologies for raining on your parade Ned, but it is not an SBDU brochure.
What it is is a Lightweight Unit (Nottingham) brochure - only the back page relates to the SBDU.
I have a genuine SBDU brochure* which as far as I am aware was only available from Ilkeston - which is where mine came from.
For the record (fiks) 653 was introduced in 1986 and superseded 531Pro.
P.S will post a few pages if any interest.
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.