Bogen tube amp with variable Damping Factor

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Hello everybody. Please is there perhaps a chance someone here can direct me to knowledge about this item which I believe is an audio amplifier with adjustable damping factor and adjustable input and output.

The amp chasis is 15" x 4" x 2" and the paint color is faded, tending to gold, copper, and brown.

(The painted label) - David Bogen Co. Inc. New York 14, N.Y.

- Model D070 -Series C-56 (series #4883 stamped in the metal). Uses tubes-5U4GB, 6BF5, EL34/GCA7, 12AX7/ECC83, 6CG7.

Rotary controls are labeled: Power Mon., Damping Factor, and Input level.

Speaker impedance slide switch for either 8 or 16 ohms.
Connector is labled: GND, COM, B, A

There is also a jumper with three positions which is not labled.

There are two large transformers labeled T3147-2 the other labeled T2123.