scratch on Rolex glass (maybe) - what to do?

[Chuckwagon]

Hello all :) I just joined to ask for some honest advice...

Today I took my Rolex watch to a jeweller shop that buys secondhand watches today as I'm thinking of selling it. I find it quite heavy on my wrist and I prefer to wear lighter watches.

Well, they took it away to the back of the shop to inspect it, I was quite worried as I could not see what was happening to it... Anyway they came back with it and said there was a scratch on the glass.

Actually at first they said there was a scratch on the dial... which scared me as the watch has never been opened since it was bought new (I am the original owner), so I know it can't have a scratch on the dial as it has never been touched inside since it left the Rolex factory... then he clarified it was a scratch on the glass. I am actually quite surprised because I thought sapphire glass is almost scratchproof and I don't own any diamonds that can scratch it.

I can't see a scratch with my eye but admittedly I don't have a special magnifying glass. I did take it to Rolex in London St James Square a few months ago to have the bracelet clasp tightened (it had become loose) and the Rolex technician examined it and did a great job, but he never mentioned about a scratch on the glass.

The watch is 6 years old so it is due its first service anyway... will the cost of the service include a replacement glass or it is an extra cost?

The jeweller said it would cost £200, and because of the scratch on the glass, he wasn't interested to buy it. I said if I took it to Rolex in London to have it fully serviced, would it be worth more and they said no. Anyway I was in two minds about selling it in the first place but I've decided that I'd rather keep it if it's not worth all that much.

Anyway the result is that I'm quite upset to find out whether there is in fact a scratch, and will it be best to take it to Rolex St James? I can go to London next week.

Thanks in advance for any friendly honest advice