This advert from a 1963 British music magazine highlights two new Watkins amplifiers: the 14w 'piggy back' Pick-a-Back, head with 12" Pick-a-Bass cabinet, and the Scout combo, also 14w, but fitted with a 10" speaker.
These two WEM amps were widely promoted in the early/mid 1960s. Neither lasted too long though. The Pick-a-back evolved into the (very similar) ER-15 by 1964, whilst the Scout was replaced by the Custom 15.
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