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Sleuthing an 8 reales cob


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  • Benefactor

Let's pretend that you are at a coin show, with lots of people milling about, and you are a world/ancient coin dealer.  A young person approaches your table and presents to you a dark, lightly corroded coin. "My uncle left this coin for me and I don't know what it is."  The coin is accompanied by a paper envelope, with no information on it.

Here's the coin:



As an experienced dealer, you can make some very quick observations.  The coin is silver and the feel of the coin, along with its size would suggest that it is a Latin American or Spanish 8 reales cob,  a hammer struck coin, as they all are.

But which mint?  What date and assayer?

With over two hundred years of producing these and subsidiary denominations by mints spanning three continents, the field is very wide.  An experienced cob collector or dealer would know that the mints often had design features to the dies and flans that can distinguish a coin as coming from a specific mint.  One major difference that distinguishes the Latin American cobs from Spanish cobs, with the brief exception being Bogota, Colombia (1622), is the presence on the young collector's coin of the arms of Portugal on the obverse shield, upper center.  That is a strong indication that this is a Spanish coin.  The 8 reales cobs of Seville do not have the Portuguese arms for Philip II, but that's another story.

Another feature of this coin is the Arabic 8, to the right of the obverse shield.  Since this is a Spanish cob, the dealer can deduce that the coin was produced from the 1630s forward, when the Roman numerals  VIII is replaced by the 8 for silver denominations, generally speaking, with Bogota and Cartagena being exceptions.  

What Spanish mint?  Attribution depends on the clarity of the mint mark.  For this coin it is there, but muddled by strike and surface condition, as is so often the case.  Spanish cobs of the 1600s, like their Latin American counterparts, have the mint mark to the upper left of shield.  The mint mark for this coin could be a R, but that doesn't make sense for a Spanish cob.  Close examination reveals the mint mark to be a monogram, MD, positioned vertically, for Madrid.


Now, for the assayer.  Just below the mint mark is what appears to be a B, but it is an odd one, because it is inverted.


With these two pieces of information, it's time to open Krause and look up assayer B for the Madrid Mint.  This mint produced shield cobs from 1620 to 1666.   Assayer B appears on cobs produced in the 1640s.  The inverted B appears in 1642 and 1643.  Since the coin lacks any portion of a date, the coin can be attributed to 1642-43.  

So, the "mystery" coin is an 8 reales cob, 1642-1643, Madrid Mint, Philip IV, assayer B (inverted), KM 120.  The coin's weight is 26.07 grams, so very probably salvaged.

Experienced cob collectors and dealers can often determine a coin's origins, even for a badly corroded one, based on flan shape.  Mexico produced barrel shaped flans in the mid 1600s.  The cobs of Mexico during the reign of Charles II are often rectangular or bizarrely shaped into almost  zoomorphic forms.  Cobs made in Madrid during the time of this coin often have an angular shape due to clipped edges done at the mint to adjust a flan's weight.  

There are yet another very distinctive feature for Mexico.  All Mexican shield cobs have ball-like ends to the reverse cross.  Even if a coin is worn or corroded to virtually beyond recognition the round end or ends of the cross clearly makes it Mexican.

Mexico, Philip IV, 8 reales, 1667 G over P.  Musi River Sumatra salvage

KM 45

25.4 grams 



Finally the Mexico City Mint apparently had a practice in place to adjust the weight of gold cobs by means of using a file on the coin's edge.  The beveling effect can be seen more readily on some coins than others.  The reverse of my example best demonstrates this bevel effect.  No other mint, as far as I know, employed this unusual technique for weight adjustment.  The large scratches were caused by the environment.  I was told when I purchased the coin that it was a beach find.  

Since most of these gold cobs are well struck, plus the fact that gold does not corrode (but the alloy can, creating a "sandblasted" effect for some coins), this feature is not an essential one in the identification process.

Mexico, 8 escudos, 1713 J.

KM 57.1

26.96 grams



So, much like ancient coins, Spanish colonial and mainland coins can pose a challenge in identifying specific features, but then that is at least half the fun! 


Edited by robinjojo
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  • Benefactor

Here's a pretty typically crude and encrusted cob, from Mexico.  This coin is part of a group of 8 and 4 reales, primarily Mexican, that came out of Sanaa, Yemen a few years ago. 

The is example is virtually devoid of any data - no mint mark, assayer or date. Only the bottom of the denomination "8" is visible on the obverse.  However, the coin can be attributed with 100% certainty to Mexico, due to the globes at the ends of the reverse's cross.  Odds are that this is a Philip IV cob.

As very crude as this coin is, it weighs a hefty 27.49 grams.


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