On most writing instruments the model number is not directly imprinted; on some 146 and 149 fountain pens it is found on the cap ring (e.g. 'Meisterstück 146'). The numbering system is historically grown: the first digit denotes the series (up to WWII there was additionally the '4' for school and stylo writing instruments; the '3xx' was not a pure pupil line but simply the third series). The second digit stands for size, the third for device type: 4 fountain pen, 6 ballpoint, 7 twist pencil. Thus 114 denotes a fountain pen, 116 a ballpoint and 117 a twist pencil.