Industrial equipment - Germany - Hearing equipment

This object is a vintage Malchus pocket hearing device, probably produced in the 1950s or 1960s of the last century.

Features of the device
Casing: A compact, cream-white plastic or Bakelite case. In this case were the microphone, the amplifier and the battery.
Brand emblem: The round metal plate with the elegant inscription "Malchus" also functioned as the grille behind which the microphone sat.
Carrying method: This type of 'pocket' hearing aid was usually worn in a breast pocket or attached to clothing with a clip.
Earphone: Through a cable wrapped in textile or plastic the case is connected to a separate earphone (often provided with a custom-made transparent earpiece).
Storage case: The whole unit sits in the original blue-lined storage folder with a zipper to safely transport the device.

Thanks to the advent of the transistor in the 1950s, manufacturers could produce this kind of compact 'pocket models,' which at the time was a huge technological advance compared to the earlier, heavy valve devices.

Found while clearing out my grandfather's belongings; I know he used it often and was very careful with it.

Unfortunately I cannot test it because I do not have the right batteries at home.
(22.5 volts for the anode voltage)

It was a very luxurious version; on the microphone the brand name is engraved; the case is lined with velvet and the exterior is made of crocodile leather.