This item is a Sperry Gyroscopic Heading Indicator, Part Number 646050 / AN5735-1. It is as-removed from a 1958 Cessna 172 (C-172). While we did do a knob-pull and assure it adjusted the face and did a 360 and watched the indicator move, it has not been professionally tested and is represented as unknown condition and assumed to be a rebuildable core. 

Please note: this unit comes with additional fittings; however, we noted they were difficult to remove and we made a decision to allow the buyer to pursue removal of those fittings.

The part is as-depicted in the attached images. This unit is assumed to be inoperative and not airworthy in its current condition. I am not an A&P and cannot speak to the state of the part. Any part numbers quoted are based on data retrieved from the parts manual. Part number verification is subject to the inspection of your A&P-IA. As with any aircraft part, your A&P-IA makes the final call as to the applicability and airworthiness of the part. This should be completed prior to installation and use.