Tons of Cash

Ten tons or some 2 million "cash coins" were recently excavated in China.   For import restrictions under the Convention on Cultural Property Implementation Act to apply, the item of "archaeological interest" must also be of  "cultural significance." With numbers like that, one wonders why there are any import restrictions on Chinese cash coins at all.  China allows its own citizens to collect such cash coins freely.  So why can't Americans freely import them from abroad as well?