The lens is easily replaced, should you ever want to. Take to a competent optician's shop and they'll do it. All it is, is a simple magnifying glass, after all. So long as they can remove the old lens, and put in a new one - it can be done.
I have an 18k rare Georgian quizzing eye! It’s coming in on Tuesday! Excited to see it up close before I put it up for a new home. I always found the quizzing eyes fascinating and shocked more people don’t collect them, as they are functional as loupes or quick magnifying glasses.