Four maritime keys, from left to right:
Deluxe Stream Key manufactured by Dentsu Seiki Co.Tokyo, Japan.
Model HK-1S Swallow, with silver contacts 6 mm. in diameter.
This company later become known as Hi-Mound.
Hi-Mound key, Model HK 703
Hi-Mound key, Model HK 704.
I understand the last two used on board of ships, but could have been in operation somewhere else.
Polish key (?) found on board of fishing vessel at the breakers´ yard.
No markings found except in the plug (Made in Poland).
Russian key found on board of fishing vessel at the breakers´ yard.
The base contains an array of coils, resistances and capacitors, with
four terminals at the back.