In times of siege everything possible was used as a substitute for metal. Cardboard was even used, although it wasn't exactly a material with permanence..

When the city of Leyden in 1574 was under siege, its government allowed cardboard coins to be manufactured with a worth of 20 stuiver. The coin had a circumference of 38 mm.

These words were printed on the coin::
Godt behoede Leyden, N.O.V.L.S.G.I.P.A.C. = Nummus obsessae urbis Lugduni sub Gubernio illustrissimo Principe Auriaci cusus.
=
"Coin of the city of Leyden under siege, defeated by the illustrious prince of Orange".