Author Topic: Is this Portuguese India coin genuine?  (Read 436 times)

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Offline naabh4

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Is this Portuguese India coin genuine?
« on: June 05, 2017, 10:22:11 AM »
This is not my coin. This is the description given by the owner of the coin:

 Indo-Portuguese tin bazarucco, ND, produced during the reign of D. Joao V (1707-1750).at Goa. Ref.: Gomes J5 01.02. Weight: 1.65 grams


Offline Figleaf

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Re: Is this Portuguese India coin genuine?
« Reply #1 on: June 05, 2017, 11:15:22 AM »
It passed my first test: if it's not in Gomes, it's probably a fake. It passed my second test: it is very similar to the picture in Gomes. (BTW, metal should be zinc - tutenag, not a problem since tin and zinc have virtually the same look.) That makes it 50/50 of being genuine :(

A faker would love to turn a useless piece of metal into a collector's item, but he'd maximise profit. By making the coin a grade better, he could have doubled his profit without raising suspicion. That reasoning tips the scale to 80/20 in favour of genuine.

Peter
An unidentified coin is a piece of metal. An identified coin is a piece of history.

Offline naabh4

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Re: Is this Portuguese India coin genuine?
« Reply #2 on: June 05, 2017, 11:23:33 AM »
Thank you Peter. My biggest concern is that this coin does not look like Lead / Tutenag. It looks more like a cast copper coin than a lead / tutenag coin. Which is why I expressed my doubts to the owner.

Offline Figleaf

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Re: Is this Portuguese India coin genuine?
« Reply #3 on: June 05, 2017, 11:42:27 AM »
Indeed, zinc (and tin) look grey, while there is a clear tinge of red in this coin. However, the light and especially the background may have reinforced this effect. Moreover, tutenag is not pure tin but a mixture of tin and anything at hand to make it a bit harder. No idea what happens if you melt a copper pot into a tin mixture.

So let's make it 66/33 in favour of genuine. The problem is that you can often show that a coin is a fake, but you can never show that it is genuine. In this case, even the experts don't agree on what is genuine, so the best filter is to look at what has been known to exist for a long time, in other words what's in Gomes.

Peter
An unidentified coin is a piece of metal. An identified coin is a piece of history.

Offline lakdiva

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Re: Is this Portuguese India coin genuine?
« Reply #4 on: December 29, 2017, 04:56:31 AM »
Take it to a jeweller and get a non destructive XRF measurement, that should give you a surface composition.
There is no need to guess at composition.

In Sri Lanka where I reside, there is jewelry store which measure a coin for under US$1
XRF's in Jewellers are fine tuned to measure gold and silver, but will give useful estimates for
other metals. An ideal way to seperate the fantasies from the real. 
See what I found about a gold coin I purchased from Spink
 http://coins.lakdiva.org/medievalgold/k1cf4t10c_adahanda_au.html
Trying to get my Archaeological Institute to buy an XRF which is more sensitive
to identify impurities.

Offline Figleaf

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Re: Is this Portuguese India coin genuine?
« Reply #5 on: December 29, 2017, 10:05:11 AM »
Good advice, but it can only be followed with the coin in hand. In this case, naabh4 was considering buying the coin only.

Peter
An unidentified coin is a piece of metal. An identified coin is a piece of history.