I see that some 'Tetradrachms' are called 'Bi Tetradrachms'. Can someone please tell me what the difference is, please? (See my Hadrian - 'Tetradrachm' or 'Bi Tetradrachm'?)
"BI" = "billion", the rather strange and nonspecific name for the silver alloy used for Roman Egyptian tetradrachms through roughly the mid 3rd century. After that, the metal had been debased to a greater degree and a new term "potin" tetradrachm is used. I don't know the etymology of the words but generally associate "potin" with "pot metal"-- whatever metals were on hand + a pinch of silver. The denomination is still "tetradrachm". The amount of silver in them declined considerably over time and by Diocletian these tetradrachms were only ~1% silver.
Thank-you, TIF. Exactly what I wanted to know. I suspected that it might refer to the metal, but it could have also referred to 'half' of something. (a denomination). Mystery solved. Thank-you, again.
TIF's answer is great but like all good information it brings up more questions. Why do we metal people feel the need to separate silver from sort-of silver from looks like silver? However, we call gold 'gold' even when it is well under half gold and give it different names including the word gold depending on what it was alloyed with (red gold, white gold, rose gold etc.). Coin people do allow 'electrum' for gold/silver alloys that range over quite a variety of recipes. Consistency is not our strong suit. Coin people have no problem using AE for any alloy of copper as long as it looks even a little red or yellow (bronze, brass, leaded bronze, orichalcum). However, 75% copper and 25% nickel is just 'nickel'. Pot metal is like canine 'mutts' in that the term tells little about the thing. Considering the messy facts, we are lucky that we have TIF to make it simple but If we posted photos of a range of these coins, it might be hard to say exactly which ones should be called billon and which silver (or something else?). We see silver coins that have not tarnished after many years like good silver should. Is anyone rhodium plating these?
Saw this in Wikipedia, seems like billon can even include plated coins...Rhodium plating...I like that. https://en.wikipedia.org/wiki/Billon_(alloy)
We are United. I have been diagnosed as Highly Dyslexic... You just have to be pragmatic and recheck yourself. The advantage is that you can read all misspellings, sentence screwups, backward Russian Cyrillic, and completely understand!
In that case, I believe my coin to be:- HADRIAN Emperor Father of Lucius Aelius, and Antoninus Pius SilverTetradrachm 25mm 11gm Obv: AVT KAI TPAI ADPIA CEB, Laureate, draped, & cuirassed bust of Hadrian right, seen from behind. Rev: ΠΑΤΗΡ ΠΑΤΡΙΔΟC, two right hands, clasped. L-IB (date - Yr. 12) around. Coin minted 127-128 A.D. Egypt, Alexandria Ref: Koln 979; Milne 1263; Emmett 848 Am I right?
ahaha, that made me smile Oh, I also smiled at somebody the other day when I mentioned that I had a touch of OCD ... and then the dude replied, "don't you mean CDO?" Oh sorry, Topcat => that's an awesome OP addition (congrats, dawg)
