For jewellery, there are two main types of counterfeiting. One common form of jewellery counterfeiting is false hallmarks, i.e. sub-alloys in which a higher proportion of gold is stamped on than is actually present. The CaratScreenPen is the best device to measure the carat number of gold within seconds. Test acids or density scales can protect against this. The other form is the use of counterfeit materials, such as wolfram carbide jewellery with gold plating, or e.g. "Autobahngold", which often consists of gold-plated brass or stainless steel. Here, the GoldScreenPen can in some cases give important indications.