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For the record (fiks) 653 was introduced in 1986 and superseded 531Pro.
Roadking.
P.S will post a few pages if any interest.
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V-CC member #584, co-founder of V-CC Lincolnshire section, member South Eastern Road Club. In the garage - 1987 Roberts(lugless)Audax, 1986 Raleigh SBDU Pro Super, 1984 Raleigh LU Corsa, 1984 Roberts Tourer, 1980 Allin Stan Butler Special, 1977 Geoffrey Butler(Cliff Shrubb built), 1976 Geoffrey Butler(Roberts built), 1975 Bill Philbrook(lugless)tourer, , 2 x v.early Roberts #107 & #127, 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. MTBs - 1988 Specialized Stumpjumper, 1988 Muddy Fox Courier(Wife's).