Coin, Mexico, 5 Centavos
1970 - AU(55-58) - Brass - KM:427
National arms, eagle left.
Bust right
Due to some minor alloy variations this type is often encountered with a bronze-color toning. Reduced size.
2.78 gr
Brass
Brass has had a variety of names over the year… It was known as orichalcum (aurichalcum) by the Ancient Greeks and Romans, Florentine or Venetian bronze, yellow copper, similor, and even tombac. Its name may vary depending on the proportions of the recipe and its origin, but the composition of this alloy remains the same: a successful and beautiful marriage of zinc and copper.
The alloy is variable in spirits and color: the more zinc dominates, the whiter its hue, the more copper dominates, the more it glimmers with golden highlights.
In its monetary form, there is evidence dating from the 1st century BC, in the area of Asia Minor, most likely in the Kingdom of Pontus. Its usage then spread throughout Asia and Europe. Augustus notably substituted it for bronze for certain dupondii and sesterces. Much later, in the 18th century, it was a popular choice for tokens. Pinchbeck (a low-end brass) was used on medals to imitate gold.
The properties of the alloy may vary depending on the proportions of metals employed, but it is well known for its great malleability and good resistance to corrosion.
When copper constitutes the majority, the patina may turn green.
An “AU(55-58)” quality
As in numismatics, it is important that the state of conservation of an item be carefully evaluated before it is offered to a discerning collector with a keen eye.
This initially obscure acronym comprising two words describing the state of conservation is explained clearly here:
About Uncirculated(55-58)
This means – more prosaically – that the coin has been in circulation but sufficiently little that its original beauty is preserved almost in its entirety. The wear is barely visible and any other defect can only be identified with a magnifying glass or a particularly keen eye. The number (55-58) indicates that between three quarters and almost all of the original luster remains.
