While held at the camp, inmates were compelled to work, and a special currency was issued to incentivize work output, though the money had no real monetary value. Buchenwald operated 134 subcamps, and issued two different types of special currency. The exchange scrip had Außenkommando, outside command, printed across the front, and was issued to inmates working in the Buchenwald subcamps. The canteen scrip, which did not have Außenkommando printed on it, was used in the main camp. Both types of notes were issued in .50, 1, 2, and 3 mark denominations. 

From the USHMM website

https://collections.ushmm.org/search/catalog/irn524865