This is a used Ergotron WorkFit-S stand for a single, heavy duty monitor (like a 43" ultrawide) with a worksurface and tray for keyboard and mouse. There is some dirt stains on the handle that I can't seem to remove. Shown in photos. It's hard to tell but stains are darker in person. I'm not sure why. Different reflection.
It is designed for monitors up to 28 lbs but not more than 29 lbs total weight with the items on the worksurface/keyboard tray. The unit includes a height-adjustable column, desk clamp, crossbar, monitor pivot, worksurface and large keyboard tray in a sturdy, professional-grade design.
It's an easy-to-install, sit-stand converter that attaches to the front of most stable surfaces. The total range of motion is 23 inches (58 centimeters) of straight vertical lift that is angled slightly as you go up instead of the traditional ones that have an arching motion due to the cheaper mechanism.