Is it possible for ADs to sell a fake Rolex?

[Gd93]

General question for anyone with knowledge that can help. I recently got engaged and my parents gifted me a stainless steel submariner that was supposed to be from 1991. They bought it from London jewelers who is an authorized dealer of Rolex, however, I was vacationing in Greece and brought it to a watch shop who said it was fake. Immediately I thought this was impossible because London jewlers is an AD. But I went home and weighed it (it came out to 125 grams) I looked up what the weight of these watches were at the time as I know the newer ones from 2010 on are heavier. I found that it should typically be 135 grams. Because of this I took it to London jewlers and the representative I spoke with assured me there is no way a watch they would sell us is a fake. He went on to appraise the watch for the amount my parents paid for it which gave me peace of mind.

Fast forward a few months and I’m getting more and more into watches and notice that many older subs have a t<25 under the 6 o’clock marker on the dial. I read that rolex did this up until 1998 when they decided to not use tritium in their dials anymore for lume. I look at my sub and it reads “swiss made” so I am going through the whole doubting process again. Sorry for the long story but I felt it was necessary. Is it possible that a Rolex AD sold my parents a fake sub? I would really appreciate your help with this as it’s been stressing me for a while. Thank you so much, keep up the awesome content