How do you put serial numbers on a liquid that is clearly divisible down to the molecular level? Are you suggesting every individual molecule gets tagged? And do you really think Ferenginar has a mint somewhere where they control the money supply? And how could you possibly catch somebody who replicated latinum?
Unless the writers created latinum as some sort of modern variant of currency so Ferengi acquisitiveness could be physically represented without thinking about realistic rules of supply and demand within the established rules of their universe *glares at camera*, it makes no sense that latinum can be replicated. Dilithium can't be replicated either.