It's a small calibration square for your 3d printer.
Just print and measure for more printing fun! I made this model a little large on the XY-plane so my measurements for calibrating the printer are more accurate.
outside: 40 x 40 mm
small beam: 2,5 x 2,5 mm
larger beam: 5 x 5 mm
square block: 20x20 mm
wall-thickness: 2 mm
total height: 10 mm
Mine actually showed me some backlash or slipping during print at 2,5mm and 5mm Z-height.