This is I guess more of a "I'm just wondering" type question for the international users of the forum. As an ex-pat from the UK from what I remember of the UK requirements they are 7.8 gram for silver, 1.0 gram for gold and 0.5 gram for platinum? Here in the Netherlands it is similar;
silver 8.0 gram, gold 1.0 gram and platinum 0.5 gram. Palladium is not yet a requirement but is an option.

Out of interest a minimum assignment is 21.00 Euro, which is often difficult to achieve in one go. Unlike the UK we have now just one hallmarking office and it is in the city of Gouda.

So internationals, what are the requirements in your country?