The catalogs list your piece as a 1/4 real from Zacatecas, one of the states that comprise the Republic of Mexico. There was also a 1/8 real with the same pattern, only smaller. Here are the weight of these old-and-interesting pieces made of brass:
1/8 REAL (OCTAVO): 4 grams
1/4 REAL (QUARTO or QUARTILLA): 8 grams
The federal government of Mexico retained its rights to strike coins in precious metal. Zacatecas is an area rich with silver mints, and the local government was not satisfied with having to settle for non-precious brass coinage. The inscription of 'ESTo.LIB.FED.DE.ZACATECAS' (Esto Libe Fedo de Zacatecas) pokes a joke at 'federal liberty'! Approximate catalog values appear below.
The ocatavo in our picture comes from Ponterio & Associates (see Stack's Bowers) where it sold for $160 US dollars in a 2010 auction.
1/8 and 1/4 REAL common date:
worn: $30 US dollars approximate catalog value
average circulated: $80
well preserved: $250
1/8 Real coins dated 1851 are rare and are worth about 3 times the values listed above. The coins dated 1829 are extremely rare.
1/4 REAL coins dated 1831 are scarce and are worth about twice the values listed above. 1/4 reals dated 1826 and 1860 are worth 5 times the values above. 1/4 reals dated 1824 are extremely rare.
Remember to read our Important Terminology page found at the top left in order to properly interpret the catalog values used on this page.