Definately a fake. There’s an earlier thread 2019 where someone saw a ring on eBay. It’s well known on the fake number “52833A”.
It is very difficult to buy authentic Cartier pieces off eBay or Instagram or wherever as they are so often fake. They even do fake receipts, fake cards, fake boxes and fake bags. The rings aren’t even necessarily gold. Unless you want to risk losing your money or don’t mind buying a fake, it’s best to buy from either Cartier or authenticated sources.
I would also suggest to buy directly at Cartier. The risk to buy a fake is big. Head down and spend the money if you really want a Cartier piece. Expensive but at least you can be sure what you have.