How can I be sure of the purity of the gold or silver supplied?
Local gold and silver bars/ingots are stamped with the suppliers “hallmark” and with either 9999 for gold (four 9’s or 99.99% pure) or 999 for silver (three 9’s or 99.9% pure).
Also, in terms of ensuring purity of supplied product the local New Zealand suppliers we use regularly exchange metal with other companies locally and in Australia and so when this happens the metal is assayed again. So if there was ever a problem with purity they would be found out before too long and as reputation is everything, this would put them out of business. They are family owned and run businesses, conservative by nature and have been around for over 30 years, supplying precious metals to private investors but also to Jewellers in NZ.
Some overseas products such as bars from Swiss Refiner PAMP come with assay certificates and individual serial numbers. These cost more then local gold and silver. For example for gold, another $45 per 1 oz bar more and for silver, a further $50 per 1kg bar. These are more readily exchangeable overseas, so depending on where you intend to sell them, may be a better option for you.