Marconi's Second Key was the first to be designed specifically for wireless work and superceeded the "Mastead" naval type whick was previously in use.  He used this key in all his experiments at the Haven station , Poole,. This led to  key patent 7777 for tuned apparatus.

Marconi's Second  Key. It did not have a model number.  (Image courtesy Fotolibra)

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Contributors and Credits:

1) Lewis Bodkin  <05bodkin555(at)gmail.com>
2) Handbook of Technical Instruction for Wireless Telegraphists.
 

Aug 1/18