Practical applicability of alternative sort of coating of contemporary copper forgeries with use of mercury only (i.e. without use of another metal such as silver or tin) has been experimentally definitely proven. This undescribed way of amalgamation coating is based on simple dipping of a cleaned copper flan in mercury. In few hours, a stable silvery layer of the copper amalgam covers the copper surface. This kind of plating was most likely used by forgers in process of plating of the copper forgeries copying parvi of Wenceslas II at the beginning of the 14th century.
Unattractive stains on gold coins – sometimes wrongly described or mistakenly understood as gold corrosion – remained in focus of increased interest of scholars especially because of development of modern analytical techniques in the last decades. It is impossible to answer the primary questions about character and reasons of appearance of these stains without deep interdisciplinary knowledge. There is also another important question dealing with prevention of these stains and possibility of their gentle removal. The presented study tries to discover what caused appearance of the dark stains on the surface of the gold medal from Olomouc celebrating handover of the rule to Franz Joseph I and what is their chemical substance, and if it could be – in this case – a result and external effect of violation of the declared fineness.
Starting with 1830, the mint in Vienna began to strike the Hungarian 20-kreuzer pieces. Later on, the mint in Kremnica continued with their production. The recent specialized literature does not discuss the beginning of the striking process in detail, and all existing minting years and varieties are not listed there. This article is focused on mapping all these coins and revision of the existing minting years of the particular types ever listed.