Monogram of Charlemagne
The monogram is a sign of identity usually formed of the combined initials of a name.
Charlemagne was known first by his German name Karls des Grossen=Charles the Great, and the Latin was Carolus Magnus.
When Pope Leo III made Charles the Holy Roman Emperor on Christmas day in the year 800 he received a more definitive Latin, one word name of KAROLUS.
Perhaps the additional "US" = great.
Charlemagne himself or those intellectuals around him designed the monogram around the new, one-word Latin name
His monogram does not read around the circle KRSL but rather KRLS, because the K goes to the diamond which has a superimposed A, O, and U written like a V. The K goes to the top part of the diamond that has the A and then up to the R back down to the total diamond which is the O, then down from the diamond to the L then up from the L to the diamond, to take the bottom part of the diamond to form the V=U then from the diamond to the S.
The Consonants are on the outside KRLS and the diamond contains the vowels on the inside of the monogram. This then is the sign of identity of Charlemagne with all the Latin letters CAROLS or Charles the Great.
As taken from "Caroli Magni Progenies-I" by: Siegfried Rosch