Prior to this CBS take-over date the plant was Levy's, Pressing Plant, Aston Clinton, part of the Levy brothers music empire, which included Levy's Sound Studios.
(Prior to the takeover, CBS UK pressings were done under a distribution agreement with Philips Records Ltd. between 1962 and Sep 1964).
The matrix on pressings is usually stamped at 12 o'clock, horizontally - rather than following the circumference of the runout, as found on Philips/Phonogram pressings.
The most obvious indicator for a CBS pressing is Λ, which is actually a faintly stamped "broken" A, which may also look like ∴ (3 dots in a pyramid) found at 9 o'clock, which is a stamper indicator. On high volume singles there may be other "shallow" letters such as B, C or F, of which one letter may appear as a broken circle or two brackets ().
At three o'clock there are usually one or two numbers; again these may also be very faintly stamped or etched.
Around 1977 the stamped matrix was replaced by a handwritten one but the layout remained the same, i.e. the symbols are at three o'clock and nine o'clock.
CBS UK contract pressing matrices may vary and be hand-etched on a radial curve (still, usually, at 12 o'clock).
The plant relocated from Aston Clinton to Aylesbury in 1980. Construction began in March 1978 and the official opening was on 20 June 1980.
The new press room then had 40 automatic Hamilton presses for LP production, and 20 SMT and MAP presses for singles.
The plant also included the printing of covers and labels, as well as the sleeving.
CBS pressed 7"s with solid centres and 4-plugs, allowing for post-manufacture dinking only. They did experiment with cut-out large centre-holes (and spiders) between March and May 1976 but had to give it up due to negative dealer feedback.