Back when I was doing this, by going to NYC and getting board certified (I think it was the New York Board of Trade), my liability insurance rates dropped.
AGS and GIA were the only ones I ran through. I sold AGS certified Diamonds, as kind of a niche to set me apart from the discounters. More expensive, but cut to Ideal Proportions.
Oh, and I have never ever used a pair prong pliers..... Gimme a hammer and a cupped tap.
Funny story, I am sitting there in the NYC Exam and we are setting stones. The classroom was as quiet as a mouse because we were setting faceted quartz cushion cuts as part of the exam.
As my instructor described it: "All of a sudden from the back of the room I hear a tap, tap, tap, of a hammer. I looked up and you were tap setting! I couldn't believe it!" Passed the exam.... LOL!