I think they might be Polish, but don't have a catalog for Polish issues to check. Top reads "National (or Peoples') Treasure" (Skarb narodowy). Bottom says something like "Exchange (or To Buy) Gold and Silver" or something similar. Polish currency is zloty. These are denominated in Marks. Maybe during German WWII Occupation? Sorry I don't know more about these!
These are gold and silver tax stamps. They are Barefoot Poland Revenues numbers 1 (1 Marek), 5 (10M), 6 (25M) and 7 (50M). Values/prices given are .50, .50, 1.00, and 1.00 (in British pounds).
From the Barefoot catalog, "This was an obligatory tax during the first years of independent Poland, to raise funds for the purchase of gold and silver, to stabilize the economy and prevent inflation. They were to be used in addition to normal revenues on documents which needed to be fiscally stamped. In practice the stamps seem to have been little used on documents and most of the surviving examples of these stamps are mint."
Your stamps are from the first series (#s 1-19) of 1919-23. The second series of stamps (surcharges) are from 1924. The third series (1924) features 4 values of the same design in new currency (Gr.), #s 27-30. Barefoot catalog says, "The use of these stamps was discontinued in 1924.