The problem is that this number says precious little about actual rarity and/or value.
You could have an item from a popular country with a 10 million mintage of which the majority was melted down and all surviving pieces will be at least scarce, sought after and quite valuable. Then you could have some piece from some soon to be under water island with a mintage of 200 and you can readily buy it from the next eBay junk peddler for a handful of bucks.