Testing marks, as we understand them, are intended to help customers make their decisions. The testing mark is intended to provide orientation aid when selecting from the various products on the market. It is nothing less than a sign of trustworthiness for a product's quality and a firm's effectiveness.
The GS mark stands for "tested safety (Geprüfte Sicherheit)".
To earn the GS mark, a manufacturer must submit its product to a testing site approved by the German Secretary of Labour.
The accepted testing site judges each product based on the provisions of the German Device Safety Law (Gerätesicherheitsgesetzes), accident prevention guidelines from the Employer's Liability Insurance Association, DIN and EN norms as well as other generally accepted rules of technology. This is combined with regular inspections of manufacturing facilities.
If all requirements are fulfilled, then the manufacturer receives a product-specific certification and may apply the GS mark onto that product. Annual inspections of the manufacturing facility are conducted to verify the continued validity of the certificate.