Above are shown the three different patterns of Preußen (Prussian) Kokarden that identify rank. The Mannschaften (Other Ranks) issue Kokarde is constructed on one piece of metal without an additional ring. The so-called "NCO" Kokarden has an additional ring with a distinctive diagonal ribbing (similar to that worn by officers prior to 1867). The post-1867 officer Kokarde is constructed of a base plate with an additional "double ring" metal ring on top.
The evolution of the Preußen Kokarde:

1842:
  • Officers, Fähnrich -75mm leather Kokarde w/ silver metal ring
  • Vizefeldwebel and below -75mm Leather Kokarde
1844:
  • Officers, Fähnrich, plus now Portepee-Unteroffiiziere -75mm Leather Kokarde w/ silver metal ring
  • Sergeant and below - 75mm Leather Kokarde
1846:
  • Officers, Fähnrich, Portepee-Unteroffiiziere -75mm silk Kokarde with silver painted ring although 1844 Kokarde used concurrently.
  • Sergeant and below - 75mm Painted wool Kokarde
1848
  • "Deutsche Kokarde" introduced worn on the left side of the helmet. Terminated in 1851.
1857
  • Officers, Fähnrich,Portepee-Unteroffiiziere -75mm Stamped metal Kokarde with silver affixed ring
  • Sergeant and below - 75mm Stamped painted metal Kokarde
1867
  • Officers, Fähnrich- New 55 mm Kokarde with "twin rings" on the silver affixed ring (Note: This could have occurred in 1871. The exact date is not yet confirmed)
  • Portepee-Unteroffiiziere -Retained the 1857 officer's Kokarde, but reduced to 51mm, what is often called the "NCO Kokarde"
  • Mannschaften Kokarden for Sergeant and below - 51mm Stamped painted metal Kokarde
1887
  • Mannschaften Kokarde for Sergeant and below receives an additional hole under the center for the M87 chinstrap mounts.
1891
  • Mannschaften Kokarde for Sergeant and below and "NCO Kokarde" receive an enlarged center hole for the M91 chinstrap mounts
1897
  • Reich's Kokarden introduced for all ranks to be worn on the right side of the helmet.
  • State Kokarden moved to the left side.
  • Mannschaften and "NCO" Kokarden reduced to 48mm.

At some point, Portepee-Unteroffiiziere seemed to have stopped wearing the 1867 "NCO Kokarde" (which is a reduced size 1857 - 1867 officer's Kokarde) and went back to wearing officer Kokarden. After this point, the NCO Kokarde was no longer used. The date of this change has not been determined.
 
Above are shown three of the other patterns of Kokarden that can be encountered. The Mannschaft issue Kokarde for Sachsen (Saxony) is round with a non-serrated edge. The Mannschaft issued Kokarde for Hessen is also round with a non-serrated edge, but has two distinct painted inner rings. The officer Baden Kokarde is constructed from one piece of non-serrated metal without an additional ring and is of a "ribbon" or "waffle" pattern. This pattern of officer Kokarde was also worn by Anhalt and Württemberg.