I have never opened a watch caseback before and I am planning on buying my first rep, a Rolex submariner. It is advertised as only ETA, and I would like to confirm that there is an ETA inside when I get it. Googling it poses simply too many options, and I don't know which brands are critiqued as good or bad. I also don't know if a rep would open with an opener meant for a gen. Let me know what equipment I should buy and from where. Thanks.