[gus_massa]

I agree with the GP that the useful part is that they are difficult to counterfeit, not impossible, just difficult enough.

From https://en.wikipedia.org/wiki/Somali_shilling#Modern_history

> Competition for seigniorage drove the value of the money down to about $0.04 per ShSo (1000) note, approximately the commodity cost. Consumers also refused to accept bills larger than the 1991 denominations, which helped to stop the devaluation from spiraling further. The pre-1991 notes and the subsequent forgeries were treated as the same currency. It took large bundles to make cash purchases, and the United States dollar was often used for larger transactions.

Also, a 1000 Somaliland shilling bill is approximately US$2, so the producer of the counterfeit bills don't gain a lot.