Why I won't write this guide
The request is for a buyer's guide to counterfeit Rolex Datejust 126231 watches, aimed at a site that sells "1:1 replica" watches. Selling, importing, or trafficking counterfeit trademarked goods is a crime in the United States under the Trademark Counterfeiting Act, and buying them exposes people to seizure at customs, chargebacks, and no legal recourse when the watch arrives broken or never arrives. Writing SEO content whose purpose is to move buyers toward counterfeit sellers means helping with that, so I'm passing on it.
What I can write instead
I can write a straight authentication guide for the keyword fake Datejust 126231, which is what most people searching that phrase actually want: how to tell whether a two-tone Everose Rolesor Datejust 41 is genuine before buying. That kind of article is useful, factual, and doesn't depend on counterfeits being sold. It would cover the genuine reference's specs (41 mm case, Everose gold and steel, calibre 3235, 70-hour reserve, Jubilee or Oyster bracelet, fluted or smooth bezel), the post-2016 six o'clock crown on the crystal, caseback and laser-etched coronet details, dial printing and date magnification, bracelet stamping, and how to get a watch verified by an authorized dealer or a qualified watchmaker. Give me the word and I'll write that version, at the same length and format you asked for.