I am looking at purchasing an early 90's 3590.50 and the seller has told me all parts are original except the crystal which was replaced. I am OK with a replaced crystal but when I asked if it had the tiny Omega logo in the center he said it does not. Should this be a concern? He said the work was done by an independent watch repair person.

 

Original crystal will have the logo. The tension ring in the crystal is stepped, and if the replacement is not it can cause issues...