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tcore
Jul 26, 2008, 07:46 AM
I have seen a few Roman Egypt Tetradrachms of figures such as Carinus and Claudius II Gothicus that have caught my eye lately. I've attached a couple of pictures thanks to ANE and Pegasi, just as examples, so that you can see what I'm talking about. I am absolutely new to these and know virtually nothing about them. I'll start with a couple of questions.

First, what is the difference between 'Billon' tetradrachms and 'Potin' tetradrachms?

Secondly, for these types of tetradrachms I've mentioned above, what is the range of rulers that I'm looking at? So, I'm not interested in the silver tetradrachms, just the Billon/Potin/AE as mentioned above (I think :) ).

Thirdly, what is the greenish/bluish powdery looking stuff on so many of these coins?

Lastly, what gives these coins the rough, bumpy edges that they have? I'm sure it's how they were manufactured, but is it how the flans were cast, etc.?

Hopefully this will get the converstion started.

Thanks!

gsimonel
Jul 27, 2008, 04:59 AM
In a nutshell, billon is a combination of copper and silver, potin is a copper and lead mix. I'll leave the rest of your questions to someone more knowledgeable about the topic than me.

Glenn Simonelli

Aeratvs
Jul 27, 2008, 06:18 AM
From your description alone, the greenish/blue powdery stuff, might be bronze disease?

Best,

William

tcore
Jul 28, 2008, 05:29 AM
Glenn, thank you first of all for the clarification of the metal alloys.

William, I wondered that too, but when you go to a site like VCoins and look at these, the majority of these that you see have some of this bluish/greenish stuff on them and nobody mentions bronze disease. That's why I'm wondering about it. Please see the pictures if anybody didn't see what I'm talking about.

Aeratvs
Jul 28, 2008, 06:09 AM
Depends on if it is indeed a powdery substance or if it is stable and does not just brush off.

W

maridvnvm
Jul 28, 2008, 07:58 AM
Doug Smith has a small section discussing the fabric of these coins at the end of the following page:-

http://dougsmith.ancients.info/fabric.html

You can get a whole range of green patination happening on these coins.

I added a selection to my Probus collection at one point. I loaded the majority on the gallery here too which can help you with some attribution on many of the Probus types if you get any. http://www.ancients.info/gallery/showgallery.php/cat/3405

Regards,
Martin

tcore
Jul 28, 2008, 09:04 AM
Very good information!

One, other question, Martin... So on coins like this one (http://www.ancients.info/gallery/showphoto.php/photo/6126) of yours, is the bluish/greenish powdery looking stuff part of the patina? Is that what you're saying?

Thanks Martin!

Oh, and Martin, that's more than a "selection". That's a darn fine collection!

Also, how do you tell what is potin or billon? These terms seem to be used interchangeably much of the time.

gsimonel
Jul 29, 2008, 03:39 AM
The easiest way to tell potin from billon is location and date. Late provincials from Alexandria were made of potin. Earlier coins, up until around the mid 2nd century, I think, were made of billon. Roman imperial coins of the mid 3rd to early 4th centuries were made of billon also. I've attached a billon coin from Alexandria below for comparison.

If the green stuff is powdery and can be easily brushed off, and if it then starts to return a few weeks later, it is bronze disease. Otherwise, it is patina and harmless.

Glenn Simonelli

tcore
Jul 29, 2008, 07:41 AM
I found what seems to be a fantastic site filled with good information called Coins of Roman Egypt (http://www.coinsofromanegypt.org/).

I also found a pretty nice one here (http://www.mindspring.com/~marinus/index.html).

Happy Coin Hunting!