frequently abbreviated into Rader, is the name given to a variety of the Albus issued by the Archbishops of Mainz, Trier, and Cologne, and by the Dukes of Juliers, Berg, etc., during the fourteenth and fifteenth centuries.
The armorial bearings on these coins were copied from the Electorate of Mainz, which include a double cross within a cir- cle; this design was easily mistaken for a wheel by the common people, hence the name.
A larger coin of the same typo has re- ceived the name of Raderschilling.
Source: Frey's Dictionary (American Journal of Numismatics, Vol. 50, 1916)