How often does one find casting sprues on Roman imperial coins? I understand they're fairly rare in general (and suggestive of a possible fake), but more common on the later bronzes. Also, do they detract from your enjoyment of the coin, or add to it as something of interest? Exhibit : In the case of this Maxentius follis from his Ostia mint, I find the sprue just a tad distracting, but not so much that I don't love it for its colors and graceful Fides reverse. Z.
They're not rare at all. Most flans were cast in terracotta molding trees, and whether the sprue is present or not depends on how carefully the flan was trimmed. One of my favorite coins is this bronze of Constans. The striking desert patina and casting flan imbue it with tremendous interest, to me anyway...
I would say they can be rare in certain series, more common in others, (like Nabatean and Judea, right John). I have bought coins before because of unusual sprues, and have not bought other coins because I found the sprue distracting. I would say, on average, a sprue on a higher grade example is a detriment because its a somewhat defective flan. However, they are grat clues as to how ancient coins were made, and in that regard I like them, kind of like the pivot holes on Ptolemaic bronzes.
Well as you say, it depends on the series, and the mint. Early Nabataeans exhibit no sprues at all - in fact, they had adopted the Ptolemaic/Seleucid technology of lathe machining to adjust their flans. By the time of Aretas IV, however, the coins run the gamut from neat round pieces, to coins with sprues, and other coins whose flans were clearly stamped out of long sheets of metal, or even scrap. Silver coins of all cultures seem to exhibit no sprues at all, which makes sense if you think about it. Why would you cast flans out of a precious metal only to file some of it down? - you'd have a bunch of silver dust carried away by the wind. When it comes to silver flans, I imagine the technique was to impress some semi-soft plaster with holes, and once the plaster dried, you would fill the holes with measured amounts of silver. This would give you more control over the weight of the coins and minimize loss at the adjustment stage.
Here's a coin that exhibits a pattern I've seen quite a few times. As the flan was broken off the sprue, some of the flan cracked off, at the sides. Then part of the sprue ended up getting the design of the strike. I don't think this coin was chipped after it was minted, because I've seen the pattern on numerous pieces. I could be wrong though...
I'd say the blank was broken from the chain/tree it was cast as a part of leaving an indented edge space rather like the other coins shown above. Then it was struck slightly unevenly causing the metal to spread out more to that side. If it is your job to separate flans, I'd guess you would tap each with a hammer or pry with pliers. Some would break cleanly; some would break off retaining a small sprue; some would break into the flan slightly like these. You could then take a file or nippers to correct the ones with extra metal but the ones with missing metal would be pronounced as "good enough for government work''. The most unusual situation is the leaving of the sprue as on the OP coin because it could have been corrected with a small nip . The ones missing metal would require remelting to correct and that would not be worth the effort. Some mints in some periods seemed to care a lot more about making round and even coins than did some others. Some collectors place a lot more importance on having smooth, round coins than others. If you get a chance to see photos of entire hoards, it is interesting to see the range of workmanship quality within the group. If your only exposures to what coins look like are CNG catalogs, you might get the idea that the quality level at the mint was more consistent than it was.
Thanks for the enlightening replies, everyone. I do think I have a couple bronzes with some rather unusual looking indented spaces that don't look like chips. They probably bear a closer look now. An especially nice desert patina on that Constans, John!
Nice looking coins, fellas ... => oh, and a very interesting thread (I'll have to take a peek at my coins to determine if they have any of these characteristics ... interesting)
Sometimes it is not easy to tell if an irregularity was from a sprue or other striking problems. If a flan mold had a leak at the edge, you might get a lump that survived striking rather like John Anthony's Constans but I really don't know. I do know that some mints in some years just did not care. These are late 190's Rome mint coins.
