I don't remember who I bought this receiver from, but it was part of a package deal, and came with a RACAL 6217E and a DEBEG 2000E. It also is known as the ITT Mackay 3020A (which has no handles on the front panel), the DEBEG 7200, the EB-3026, and the EB-3028.
An entire manual for a 3020A is linked here.
Various parts of the manual are linked below:
Front Matter and Contents 2.2 MBytes Section 1: General Description 1.6 MBytes Section 2: Installation 633 KBytes Section 3: Operating Instructions 5.9 MBytes
Section 4: Technical Descriptions Section 5: General Service Information Section 6: Card Test and Setup Instructions Section 7 (partial): front panel diagram and main chassis wiring diagram
The 3020B is a rack-mount HF receiver, 150 KHz to 30 MHz, vintage 1980 or so, intended for shipboard use in applications where the frequency didn't need to be changed very often. It is definitely not a band-cruiser, but is more like the R-1051.

I suspect that it isn't intended as the ship's main receiver, as it has no provision for one-touch tuning to either 500 KHz or 2182 KHz, which were the distress frequencies when the receiver was built.

It has four bandwidths (0.4, 1.0, and 2.0 KHz, and a "WIDE" position).

It supports AM, CW, USB, and LSB reception modes, has a switchable front speaker, headphone jack, a preselector, selectable FAST/SLOW AGC, and a variable-frequency BFO. The front meter can be switched to show RF input level or audio output level. An attenuator can be inserted between the antenna and the front end, using a front-panel switch.

Tuning is in 100 Hz steps, using front-panel lever switches, one switch per frequency decade. A rotary control is provided for fine tuning.

It would have been *so* easy to go to the next step, and replace the lever switches with a keypad to control a microprocessor. As things stand in the original design, the BCD inputs from the switches are decoded to provide input to the two synthesizer loops. It would seem to be "trivial" (for some value of "trivial") to replace the switches with a microprocessor, keypad, and so on, to provide the same inputs as the switches do. Memory would be a trivial addition, and very useful. Unfortunately, there is no nice way to select mode and bandwidth using computer control.

Since the switches plug into a connector in the motherboard (or baseplate) of the receiver, it shouldn't be all that hard. Yes, I know, famous last words.

The address in my installation and operation manual is:
2912 Wake Forest Road
Raleigh NC 27611

and the date on the manual is

October 1973 (Issue 4)

Parts also are pretty much unavailable, as are extender cards, extension wiring harnesses, and the like. Except for the printed circuits, this rig is built of COTS parts, and the cards would make it fairly easy to work on if you had the extenders.

For the theory of operation, click here.

Receiver front view

ITT-MACKAY 3020E HF Receiver, from the front.

The second mixer card.

This is the second mixer card, which converts the first IF signal down from 90.2 MHz to the second IF for detection.
AGC Amp.

The Automatic Gain Control amplifier card.

AM and product detector card.

The AM detector and product detector card.
Audio amplifier card.

The audio amplifier card.

IF amplifier card.

The intermediate frequency amplifier card.
The information filter card.

The information filter card.

The loop translator card.

The loop translator card.
The low frequency reference card.

The low frequency (8.000 MHz) reference card.

The major loop analog card.

The frequency synthesizer major loop analog card.
The minor loop analog card.

The frequency synthesizer minor loop analog card.

The minor loop divider card.

The frequency synthesizer minor loop divider card.
the RF section card.

The RF (Radio Frequency) section card.

The buffer card.

The buffer card in the frequency synthesizer.
The variable divider card.

The variable divider card in the frequency synthesizer.