This is a classic HSI (horizontal situation indicator) for a civilian aircraft. It uses a vacuum-powered gyro and is powered by a standard 14/28V DC aircraft bus. It's not in great shape, and is much cheaper than the defense industry aircraft parts that we usually work with. However, it was easy to get it powered up and even get the compass card to move. A pinout for a very similar model can be found at the bottom of this page. All the pins we tested (power, backlight, etc.) matched up fine. This device appears to have been superseded by the Century Flight Systems NSD-360A.
Applying power to the illumination pins and power pins caused the HSI to light up and caused the compass card to rotate a bit. As the unit is moved, the compass card rotates due to gyro motion. It still needs vacuum power to work properly.
Visit the links below to download the manuals for similar/equivalent models of this product.