[Source: Rolex Forums]

The very rare Rolex At Daytona 24hr does exist.. Rolex has sponsored Daytona Speedway Races sine 1991, and gives class winners a presentation Rolex.

Inscribed on the back is:

WINNER
ROLEX
At Daytona (date) 24

These are very rare and only came in Stainless Steel, so any exotic metal example is likely a fake. Also, many are engraved “Rolex AD Daytona”, which is nonsense and fake too.

Here is a page from the Antiquarium Catalogue of a verified and auctioned authentic Winner Daytona. Note that location and size of the Winner engraving. There are some very good fakes with correct wording, but the Winner is smaller and in the wrong location: