This amp is a Contessa CA-15 Mini Bass amplifier, similar to both the Bartell CA-10 and the Natural Music Guild CA-15 guitar amplifier.  It uses the same tube lineup as the CA-10: (2) 12AX7, (2) 6V6, and a 6CA4 with controls for Bass, Treble, and Volume.  Interestingly, it uses a 12" speaker for a bass amplifier.  Here's the schematic for it in case you need one for a repair: Contessa CA-15 schematic

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