It's missing the battery cover and instructions, but it works!

I have two of these, but one is missing the battery cover.

The following exerpt is taken from Electronic Games: Design, Programming & Troubleshooting, McGraw-Hill, 1979:

Technical Description     Code Name: Sector contains a single integrated circuit. This is a custom-make IC which Texas Instruments has designed specifically for Parker Brothers. Based on the TI family of TMS-1000 microprocessors, this IC includes a RAM which can store 64 four-bit words and a ROM which stores 1000 eight-bit words. Also included in the iC are all of the LED drivers. Eleven controls can be reached by pressing a small, recessed button with a ball-point pen. One control adds complexity to the regular program of evasive tactics of the hidden submarine. The other displays the submarine's location and heading.

The game is described in U.S. patent 4,171,135.

Click on the image below for an advertisement that ran in Popular Science magazine in the late 1970s.

From Consumer Reports magazine, November 1980:

In Code Name: Sector, your mission, should you choose to accept it, is again to seek and destroy a submarine. Unpack this tabletop game and you're faced with a multicolored playing area about one foot square that looks like a topographic map of a piece of ocean floor, complete with grid lines. A control panel consisting of compass rosette, illuminated display, and various push buttons rises at one end of the playing area.

The game starts with four destroyers at one corner of the ocean, all bent on being the first to find and destroy the enemy sub. Meanwhile, the game sets the invisible sub on a random straight-line course. Each commander can use the buttons to move a destroyer varing distances in varying compass directions, keeping track of the ship's course on the playing area with a colored crayon. A press on the panel's RANGE button discloses the ship-to-sub distance, but not the direction, on the display.

As each destroyer moves, the exact track of the sub becomes clearer; the problem is then to maneuver into firing range and drop a depth charge. But take care - if you miss, the sub will fire at you and your evasive action will take you far off course.

The toy's display serves up the location of all four destroyers, on request. An EVASIVE SUB button lets the sub change course. If the game has baffled you, a SUB FINDER button will disclose the enemy's position and heading. The game can be set to allow a single player to command either the entire fleet or any fraction of it. A TEACH MODE button takes beginners through the strategy and tactics of an entire mock battle.

Consumer Report's panelists found Code Name: Sector a time-consuming but highly enjoyable thinking game for teens and adults. Criticisms are minor: the course-marking procedure was untidy, particularly when the crayons became blunt. And the crayons broke.

From Time magazine, December 26, 1977:

A couple of years ago an extraordinary little group managed to get a shoe in Parker Brother's door: a Cambridge astronomer named Robert Doyle, his wife Holly, an astrophysicist who taught at Harvard, and her brother Wendl Thomis, a New York computer software expert. They had given themselves a name, MicroCosmos, like a rock group, and what was more interesting, they had an idea: the use of computers in games. Invited back, they brought a working model of the gadget that became Code Name: Sector. Doyle wants to make a million dollars so he can afford to write books on astronomy and invent on the side.

Wonderous as they are, the new games are not without their flaws. Code Name: Sector, the submarine chase game, has a dandy digital readout, for instance, but the courses of the sub and the pursuing warships must be drawn on a chart with a wax crayon - which, as all twelve-year-olds will recognize, is not exactly state-of-the-art technology.

This may be the oldest all-electronic handheld game.