Bruno: Very good question. I don't have an answer with respect to IR92 plates. However, to add to the discussion/confusion, line pattern front plates with the Koenig motto exist with and without the double fold in the scroll. On page 561, Volume 2 of The German Infantry from 1871 to 1914 an Oldenburg IR91 helemt is shown with a front plate having the double fold scroll. I have 3 Oldenburg infantry helmets all having Koenig plates without the double fold scroll.
The old pattern grenadier front plate (line style eagle with Koenig motto and "FWR" cypher instead of "FR") also appears to exist both with and without the double fold scroll. The double fold scroll version is most often seen. An illustration in Moritz Ruhl's Die Uniformen der Deutschen Armee, volume 2, Leipzig 1910 illustrates this style plate without the double fold scroll. Admittedly, this illustration is a drawing and not a photo of an actual plate.
Ulan regiments 1-3 also wore a front plate in the configuration of the old style grenadier plate. The double fold scroll style is by far the most common. The photographic sheets of front plates published by Moritz Ruhl show a photograph of a plate identified as Ulan regiment 1-3 without the double fold scroll.
I suppose all of the above means that the "Fuerst" front plate could exist with either style scroll.
Reservist1