Gold Testing at Pawn Shops: What to Know & Potential Issues

Question
I took my grandmothers ring that was passed down to me to a pawn shop to have it tested to see what gold it held.The guy used a new gold tester machine.The guy rubbed and rubbed in the same spot for about 2 or 3 min, he told me nothing an did not seem to only know the machine was jumping around an it was 14 or 18kt white gold.Then I noticed him rubbing the edge of the ring where he had tested it with his fingers an he handed it back to me.
When I got home looked under my loup there was a line where he had been rubbing with this machine an the gold was eat up with scraches an gold worn away. He some how damaged my ring , now can these gold testing machines do this. I would not let anyone use acide as I heard it could damage gold an thats the reason I found this pawn shop with this elect machine I heard they could not damage gold but my ring is damaged why?? Thank You Sammie

Answer
I answered this before...?
sorry I am not familiar with a gold testing ,achine...
the acid method does not really scratch your ring...just the smallest rub on a soft stone leaves a mark on the stone..the acid is then put on the stone and by the color will determine
Karet ...I have never heard of this method leaving a permanent sctratch?
regards rolfe