This draft standard classifies the control rings and includes their diameters and circumferences. The control rings are required for adjusting rim circumference gauges to DIN 7839.
DIN 78001:1994 history
1994DIN 78001:1994-07 Rims; control rings for the adjustment of rim circumference gauges
1994DIN 78001:1994 Rims; control rings for the adjustment of rim circumference gauges