Post Independent Costa Rica (1839-1857) whilst under the reale/escudo system saw shortages of coin and foreign coins considered of good weight and metal content were stamped. This included GB sixpences and shillings - I think the shilling was considered the equivalent of 2 reales, or a quarter of the "piece of eight"/dollar/peso. See Baldwin Sale NYINC 7 January, 2015: Lots 1074 & 1075 for examples of 6d and shilling