Owner Comments:
Purchased on 4/22/2012.
This is a 5-year design type coin, produced from 1816-1820.
Keeping track of monetary conversion in the German states can be somewhat complicated. The Hannoverian Thaler at the time this coin was minted was the standard of trade in the state. The Hannoverian Thaler was broken further into 36 Mariengroschen, and each Mariengroschen was further broken into 8 Pfennig. To complicate matters, the Hannoverian Thaler was only 3/4 of the Conventionsthaler, which was the standard of currency of the Holy Roman Empire. The Conventionsthaler was based on the even older standard of weight of the Cologne Mark at a rate of 10 Conventionsthalers equals one Cologne Mark (note that this "Mark" was a standard of weight -- not a currency per se -- defined in the late 1400s and equivalent to a modern day weight of 233.856 grams).
Some useful equivalencies relevant to this coin are thus:
1 Hannoverian Thaler = 3/4 Conventionsthaler = 36 Mariengroschen
1 Conventionsthaler = 48 Mariengroschen
1 "Mark" = 10 Conventionsthalers = 480 Mariengroschen
So, to make sense of all of this history helps to clarify what exactly this coin would have been worth in 1820. A denomination of 3 Mariengroschen, was equal to 1/16 of a Conventionsthaler, and equivalently 1/160 of a "Feine Mark". Thus, we make sense of the reverse inscription "160 Eine Feine Mark" or "160 per fine Mark" (remember, the horse is actually the reverse of this coin).
Using some modern-day standards, we can see that this coin should then contain 233.856 / 160 grams of silver. This calculation equates to 1.4616 grams. The coin total weight is 3.34 grams, of which from the above calculations 1.4616 grams should be silver (43.76%). The published specifications of the 1820 3 Mariengroschen coin are:
Diameter: 20mm
Weight: 3.34 grams
Fineness: 0.4370 Ag.
So, in summary, in the end it all works out pretty close to what the numbers say it should. I'm sure it's just a familiarity issue, but this kind of conversion makes me thankful for our currency system of the same period. At least for my brain, decimalization seems to be the way to go! The unified Germany of the 1870s did eventually move to a decimal system, and as they say, the rest is history.