Here is my recent surplus sale find: a Sony CCP-1300 cassette duplicator. It dubs both sides A and B simultaneously at 16x speed. Even though it's only in mono, I suppose I
Telex Copyette 1 To 3 Cassette Duplicator-Mono | PSSL ProSound and Stage Lighting
Telex Copyette 1-2-1 Mono Cassette Tape Duplicator Copier 300350000 for sale online | eBay