A sound recording can be found on YouTube. Since the recording is dated 27.04.1935, it can only have been recorded with a device of the K1 series, probably the 5th replica device
https://www.youtube.com/watch?v=OA1oDxRo_lI
A 'real' photo can be found in the Radio Museum: https://www.radiomuseum.org/forum/aeg_k1_magnetophon.html
Manufacturer: AEG
Year of construction: 1935 (only 4 units built)
Motors: 3
Tubes: 3 units (AF7, AL4, AZ1) [unconfirmed specification]