One dot for the right eye and two dots for the left is a common convention, intended primarily for the maker whilst working on them (since most patients only require one artificial eye, so would kind of know which side to put it in!). Bilateral prosthetic patients might have raised dots on their prostheses (a bit like Braille) to help them feel for the correct eye. These dots, however, number more than two and are coloured. It is possible that they are intended as an indication of the iris colour, perhaps in a fitting set. In such a scenario the practitioner has a stock of ready-made eyes and needs to select from this stock the one most likely to suit the patient before him. Alternatively the maker might be making eyes for several patients at any one time and need a way to keep track of them in his or her workshop until they can be issued to the patient. It has been pointed out that the dots would be invisible when the eye was in use.
Can any of our readers either confirm one of our theories or provide another explanation?