(Maus Ma) - "Mouse" straight key used for Krigsmarine (German
Navy) signalers training. On top of TKP straight key there is blinker
installed which provides for changing color in the four openings from black
to white following hand manipulation. We suggest that such key assemblies
were employed in Krigsmarine schools to raise up skills in visual Morse code
reception used by sailors. "Maus Ma" is our informal abbreviation.