You say you have sanded it already
Changing a crystal via a watchmaker isn’t very expensive. For the cost of your Maguires, Polywatch, and time, you could have paid to get it swapped.
Finding said crystal will require some research and digging. More than likely you can find one on eBay. I’ve found it’s easier to source it first and then bring it to the watchmaker for a swap. The replacement will look like new and he just as good if not better than the original.
from the front. First, who is going to try to sand it from the inside? Once sanded, how would one go about polishing the concave surface? What are the chances you’d sand right through the crystal? And even if you didn’t sand right through it, how long would it be before there is a gaping hole in the crystal? Would a replacement crystal be as good as the original? With the original in the condition it is in, my answer would be, YES!
