On another forum, a friend posted that he killed his chrono with a stray gas check a couple of years ago.
I did not enjoy the idea of another $100 that could be spent on powder and primers going to replace my chrono, so I made some shooting glasses for it.
Home Depot sells a very small piece of Lexan, [do not get Acrylic], about $5.
I cut a piece, folded it with a heat gun and then cut another piece to double the front and attached it with some very short sheet metal screws and mounted it in front of the chrono with a couple more screws.
Several weeks ago, a gas check made a 1/4 moon notch on the upper left side, today one hit solidly and is still buried in the Lexan.
I am going to make a new one, but this time, with 3 layers, not 2.