Äskulapstab
A trademark became a symbol of individuals' professional qualifications to perform a particular skill by the 15th century. For example, the Rod of Asclepius on a physician's sign signified that the doctor was a well-trained practitioner of the medical arts. Simple graphics such as the caduceus carried so much socio-economic and political weight by the 16th century, that government offices were established throughout Europe to register and protect the growing collection of trademarks used by numerous craft guilds.