This might be useful in identifying the device.
This appears to be part of a somewhat different version of the Elwood Distortion Lens Board, an accessory for the Elwood enlargers. In use, the print or easel & print was mounted on a similar pivoting platform called the Elwood Swing-Tilt Table that rested on the baseboard. Both the lens pivot and the easel pivot allowed rotation to adjust the tilts in whatever orientation was needed.
The Distortion Lens Board is shown and described on page 9 here, while the Swing-Tilt Table is shown on page 11. The description and use of these are described on pages 9-12.
http://www.cameraeccentric.com/html/info/elwood_1.html
The one shown in the ad appears to allow the upper part to rotate in the base. The horizontal screw below the handle likely locks the rotation in the desired position.