This is exactly the case! Some cultures used owls just because everyone knows that good money has owls on it. The fact that the style, weight etc. was completely different was of no importance. There are even a few copies made for local circulation where the silver was better than the coins being copied. The intent was to provide currency, not to fool people. I wouldn't put too much weight on capital punishment being a sign of something being taken seriously. In much of history you could get killed for hunting without a license or something equally odd by today's standards. Counterfeiting with coins better than the official would get you into at least as much trouble since you would be treading on the royal perogative to issue coins. Another point: In 99% of cases ancient/medieval coins were made with the proper value in metal no matter what metal was being used but there are a few examples of a ruler cheating in the process. My favorite example is when the 1662 Russian authorities decided that they did not need to waste silver by putting it in the coins and that copper would do equally well. For more information, search "copper riot" to see how that went over. Today we accept paper money like it was the way things ought to be but for most of history messing with the money required having a good size and well paid army ready to silence any complaints. Compare the weights of Roman denarii issued in the first year of most ruler's reigns to the ones from the year immediately preceeding that; usually they started off with a silghtly better product. This is no accident. I remain open to posting of examples of diameter being more important than weight. The more I think about it, the more trouble I'm having finding examples where it made much difference. Late Sasanians did get carried away with the big thin coins but even those seemed to be equal in weight to their chunkier cousins so it is hard to accept it as an example.
Heck, look at the first coins ever minted and you will see government stealing. The first coins were supposedly of naturally occurring electrum, but when analyzed have less gold and more silver than natural electrum does in that area. Governments cheat their people, the bigger the government the more they think they can cheat. The effect Doug alludes to is so well known, of new governments issuing good coins then immediately start debasing them, that it is used to determine chronology of coinage throughout history. If ever in doubt, the lower quality coin came after the better one. I put together a display of Chinese coins once showing this pattern over and over again for a show. I thought it was cool, and maybe the 4 people who looked at it thought so too!
I think the Sassanid has more to do with their lack of silver, and hammering out old and contemporary silver coins, than a real desire to have large thin coins. After a time they became accepted shape of money, even leading to all Islamic coins of the same design, but I think initially they were shaped that way simply to use existing coins and ensure there was no trace of the undertype. Metallurgy tests have traced the silver to first Parthian issues then Roman ones for many Sassanid issues.
Interesting. How do we tell coins were hammered rather than remelted? Do we have Sas. coins with recognizable Roman undertypes?
To a large degree there was another reason that happened. During a ruler's first year of reign they knew little about the actual goings on in the kingdom. And the coins they issued were always as per spec. But during that first year they invariably found out that the previous ruler had bankrupted the treasury. Not knowing what else to do to solve the problem they would debase their currency as that was the easiest method. Of course there were some rulers who would inheirit a sound treasury. But then, usually through mistakes of their own over the years, they would find themsleves broke or nearly so and the debasement of currency would then begin. Some even went so far as to debase the currency. Then shift back specified fineness, only later to debase it once again. Oddly enough, it really wasn't always that the ruler was trying to cheat anybody. Most often it was economic conditions that were totally beyond their control that dictated what they had to do with their currency. Pretty much just like it still is today.
I will try to find the passage in one of my books. It details a mint operating and the fact the feedstock was other nations or old coins from the Parthians. You do not see undertypes, since that was the point of hammering them out, to obliterate any undertype. I believe they saw other nations restriking of coinage, (Bar Kochba maybe), and saw the imperfect results. Also, like I said, metullurgy tests show trace elements tying many Sassanid coins to other issue. The Sassanids did have some silver, and imported raw silver from other places, so this isn't completely the way they did all of their coins. I do think it is how Ardashir started minting the drachms though. Not his Tets, which were made at Parthian mints and were debased. Maybe this practice went away in later Sassanid issues, I do not know. It is reasonable though that by then "money" was big and very thin, so of course all later rulers continue the practice. Its amazing how quickly people get used to a form of money, and anything else causes grave concern. Think how weird different shaped and colored bills would be to us today, and this is fiat money. Ancients constantly had to worry if the government was ripping them off, so any change was more important to them.