The box is made from pasteboard and covered with a printed paper sheet. The red rings on the box match the red rings on the valve and indicate that this is the HF variant. The box is 74 mm square and 130 mm tall. We also have a later box that is smaller.This early box suggests three uses for the D.3HF including detector. A year later in 1925 the white ring detector variant D.3Det was introduced and the later D.3HF box omits the use as a detector.
 
 
 
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