I just received a Ptolemy II tetradrachm with a feature I've seen before and long wondered about: the reverse is concave (bowed in), and the obverse convex (bowed out). This isn't post-strike damage or metal flowing around the edges of a die. The entire surface is evenly bowed. The strike appears to be even, so it isn't a matter of the reverse die being worn on the edges or anything. The only thing I can think of is the celator actually engraved the reverse into a curved die. That would seem to be very difficult to do, and I wonder why they would bother. Any thoughts?
Ancient coins were struck on the reverse facing up, most every struck coin will have a slight curve from striking. I can only assume this is what you are seeing without a photo.
I second David's post. As the flan diameter gets larger it becomes vey pronounced. You see it a lot on Seleucid tetradrachms as well when they get into the 27-28mm range. Here is a Seleukos I get with a nice concave reverse.
I never noticed that. I just checked some larger AR tets, per @TheRed advice, and you're both absolutely right, it is quite noticeable in Alexander IIIs, for example. It doesn't seem to be the case with the huge Ptolemaic bronzes though, which look flat to my eye. Maybe something to do with how silver cools?
Ancients were struck in that fashion (except possibly some Byzantines and others that I am unaware of), just might not show especially on Roman coins. Its just the physics of striking with a hammer and die. A very thick coin has to be hit much harder to become concave and will probably just split, while silver is much more malleable.
There is no statement you can make about 'ancients' as a whole. The 'fabric' of coins differs from place to place and time to time. Remember the first Greek coins were made 2000 years before the last Byzantines. Septimius Severus was about as long after Julius Caesar as we are after George Washington. It is important to learn what is normal for a coin type and expect specimens to fit into those characteristics. Certainly there are some coins made with domed dies which probably worked better when pushing a lot of metal into a high relief obverse portrait die. http://www.forumancientcoins.com/dougsmith/fabric.html My 1999 page needs updating. I have better coins to illustrate the point now.
Working under the handicap of soft tools and no magnification wasn't enough of a challenge, they needed a curved surface as well? And I thought I couldn't be more impressed with the talent of these celators.
A very curved eastern celtic (thacian?) tetradrachm from the lower Danube area imitates issues of Philip III of Macedon. Obv: Stylized head of Herakles right (nose right) Rev: Zeus enthroned holding a bird Domed dies? this certainly would have pushed a lot of metal into a high relief (and low detail) head of Herakles.
The reverse of Agathokles tetradrachm has a pronounced concavity. The excellent centering and strike combine to reflect the light in a wonderful way, highlighting the devices. SICILY, Syracuse. Agathokles (317-289 BCE) struck 310-305 BCE AR tetradrachm, 17.40 g, 24 mm Obv: head of the nymph Arethusa left, wearing grain wreath, earring and necklace; around, three dolphins; under, monogram (NK?) Rev: ΣYPAKOΣIΩN, fast chariot charioteer leads to left, holding reins and kentron; above, triskeles; in exergue, monogram Ref: Ierardi 12 (O2-R8); SNG Copenhagen 573 var., SNG ANS 637 https://www.cointalk.com/threads/ancient-adventures-in-bidland-agathokles-tetradrachm.243930/
Yep, this Seleucid tet is concave: Here's a more traditional view: Cleopatra Thea, Queen of Syria, with son Antiochus VIII. Seleucid AR tetradrachm, 15.85 gm, 27 mm. Antioch mint, 125-121 BC. Obv: Jugate busts, r. Rev: ΒΑΣΙΛΙΣΣΗΣ ΚΛΕΟΠΑΤΡΑΣ ΚΑΙ ΒΑΣΙΛΕΩΣ ΑΝΤΙΟΧΟΥ, Zeus Nikephoros seated l., holding lotus-tipped scepter; IE outer left, A under throne. Refs: SNG Spaer 2437; c.f. Sear 7135. Notes: Ex-Henry Clay Lindgren. An obverse die match to an example sold in Baldwin's, Dmitry Markov and M&M Numismatics New York Sale IX, January 13, 2005.
In order to reduce or even completely avoid slippage of the dies, the surface of the front (averse) die was often slightly concave and the surface of the back (reverse) die was slightly convex! If planchet is between smooth dies there is a higher change of slippage/die shift!
