Misprint under French administration

After World War I, when the Saar region, an important location for the coal and steel industry, was placed under a League of Nations mandate and under French administration, series of postage stamps with views of the Saarland were issued. The highest nominal of 25 Deutsche Mark showed the smoking chimneys of the Burbach ironworks, which illustrates the enormous importance of heavy industry at that time. While nowadays states are courting for battery and chip factories in order not to be dependent on fragile global supply chains, coal and steel production had the importance to provide the materials for armaments at that time. How priorities have changed. 

The French administration did its utmost, of course, to connect the Saar region economically to France; thus, the gradual introduction of the French franc took place from the end of 1920/beginning of 1921. The existing stamps in Mark currency were overprinted with the new value in Franc. The inverted overprint shown here was only applied (by mistake) to a sheet of 20 stamps. A small underrated rarity that one has the opportunity to acquire every few years.