Before 1989 the height of the Brocken was recorded in almost all the relevant maps and books as NN. A survey of the summit at the beginning of the 1990s based on the current reference system, however, gave the height as just 1,141.1 m. In order to provide a reference point for the old data, in the mid-1990s granite boulders were set on the highest point of the Brocken, which not only matched the old given height, but exceeded it by about a metre. A bench mark of 1142 m was recorded on the summit stone. This height on the upper plate refers to the line on the lower plate.