Authenticate please? Not sure about back

[G553]

Hi everyone,

I just bought this Rolex off of eBay from a credible seller (link here: https://www.ebay.com/itm/172249281315). The watch looks real to me except for the back case, which has "STAINLESS STEEL" engraved into it. I thought that Rolex watches only had plain case backs, so I am a bit concerned about this...

The watch did come with a certificate of authenticity from watch spot.net.

I know that the diamonds are not original to the watch but like them a lot, just more concerned that the case back was switched. The watch has a good heft to it and there's no ticking or weird sounds coming from it either. Any help would be greatly appreciated! Thank you so much:)