Basic hot shoe attachment that puts small iron sights on to help aim long lenses. The distance is pretty short and it is nonadjustable, but it's better than nothing. From experience a proper red dot sight is much more useful, although it does take up significantly more space. The dots are 1.75mm, and are filled by sticking some alternate color filament into the holes and sanding flush.
The author marked this model as their own original creation.