German, Rothenfelde Salt (Potash) Seal, Image & Found by Haico ten Breul.
Found in the Netherlands near the German border, 21mm.
Prancing horse // ROTHE(N) / FEL(DE) / SALZ
Identified by Philippe Lanez & Paul Cannon.
Paul Cannon, "I believe this seal can be read as ROTHE[N] / FEL[DE] / SALZ. The other face has a prancing horse left with possible traces of crown above, representing the Dukes of Brunswick. This is a salt (potash) seal from the mines at Rothenfelde in Germany."
See also Ducal Standard 1866?-1884?, "The standard of the dukes of Brunswick given by Siebmachers Wappenbuch 1878, shows the white horse on a red cloth.
There could be an explanation for the change in duke Wilhelm's standard. In 1866 when war between Prussia and Austria threatened, Brunswick did not support Prussia in the Bundestag June 14th 1866 and wanted to stay neutral. Soon after however it went over to the Prussian side. As Duke Wilhelm's standard with its triangles was rather Austrian in appearance, that could be a reason for changing it.
On the other hand, according to Norie and Hobbs 1848 Hanover used the same standard with the horse (in yellow, which is heraldically not correct so probably a mistake). As Hanover was annexed to Prussia in 1866 it is also possible that the Dukes of Brunswick wanted to continue the then already more than 1000 years old tradition of the Saxon Horse (Sachsenross), which is found in northwest Germany, the Netherlands and in southeast England. This would be consistent with the use of the horse by Duke Ernst August after 1913."