1923 Costa Rica On 1893 Host Coin

The denomination was changed due to rising inflation throughout South America, combined with the same post-WWI rise in the price of silver that hit everywhere else, which saw silver removed or reduced from the coinages of many countries around the world at that time. Britain, for example, dropped the silver conitent of their coins from .925 fine to .500 fine in 1920. The Costa Ricans apparently thought that it would be cheaper and easier to temporarily withdraw, overstrike at double-face-value and then re-issue their old silver coins, rather than withdraw them completely and issue replacement coins.