Obsidional Coins, or Siege Pieces, as they are generally called, are stamped pieces of metal struck during sieges or by beleagured cities, when the customary money became scarce. They frequently represent a fictitious value, and a promise of redemption at some future time. The subject cannot be treated here in detail, but conf. Mailliet.
See Also: Obsidional Coins
Source: Frey's Dictionary (American Journal of Numismatics, Vol. 50, 1916)