We bought some new optics benches for the lab. They came with lamps, but I needed an object that could be used for creating images with the lenses. The light source has a 50 mm holder, and the lens holders are also 50mm, so I created a simple 50mm disk with a typical asymmetric cross pattern that could sit in front of the light at act as the object.
The arrow is 12mm high, so magnification can be determined easily by measuring the image size (in mm) and dividing by 12. The asymmetric pattern helps show whether the image is upright or inverted.