convention-coin

from The Century Dictionary.

• noun A German coin adopted by most of the German states in 1763. A Cologne mark of silver, 13 loths 6 grains fine, was coined in 8⅓ rix-dollars.
• noun A German coin struck according to a convention of 1857 between Austria, Prussia, and other states. A mint pound or 500 grams of fine silver was coined into 30 thalers or 52½ gulden.