quick question. I love stones and I must admit I can not stop buying them online. some times on e-bay, some times in vintage shops as second hand jewelry. so I am very bad here and opportunistic I know... as I am really relying on my general knowledge and 6th sense, or 7th ..... I was very lucky couple of times but now I decided to make it easy and get myself electronic tester. did anyone had experience with those? what would be recommendation. I think after me long looking at options I found this one best Presidium Duo gem tester (model PDT-S7) ? any reviews? Thank you in advance!