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First Introduced

    
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The date information presented in the general tables is for the first recorded use of the Type designation. If a designation was re-used at a different time it will be identified differently to avoid confusion. e.g. PA.1 P.A.1 and PA1.

Further complications. In some cases two or more manufacturers introduced the same type at the same time, as when meeting a government procurement specification. In other cases one maker could introduce the type originally and only when the demands of industry required would multiple suppliers produce the valve. Thirdly, the makers could use their own designations at first for the same design and later arrive at a single designation.

In the text of an exhibit we will present both the specific makers introduction date, if known, as well as the date of introduction of the Type designation. In the case of American designs on B7G bases, European manufacture of such miniature valves followed some years later. The Mullard EF95 from 1952 is identical to the earlier American 6AK5

In short, be prepared for two introduction dates - one for the Type designation and a second for a particular manufacturer to begin production of that Type.

Allan, Curator

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