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The original amplifier had so called DIN plugs (1958) as inputs, after 1960 they changed to jacks. The Beatles used this amp, rated at only 40W. Maybe they brought it with them when playing in Germany on the Reeperbahn?
Sounds much like an old Fender, just not as sought after. According to some it was based on the same reference amplifier (found in a tube manufacturers handbook) as a Fender that was sold 2 years later.
Specs: Output 40W (Sinus 32W) Speaker output (selectable) 100v (310 ohm), 6 ohm, 15 ohm input sensitivity 5mV - 0.5V
Was often accompanied by a tape echo called Echolette NG51-S.