How Low (On Silver Content Below 70%) Can You Go?

Some of the Polish ones might be known - which ones they are? Maybe some of the others too.

For the antoniniani there's an ongoing theory that the XXI (or, at some mints, KA) on the coins after Aurelian's reform is intended to represent a ratio of 20 parts copper to one part silver (which rounds to 0.048 silver fineness, or 5%). The measured silver content apparently roughly matches those numbers.

Not sure about the eloquence (but thanks for the compliment ), but if we look at French coinage (the only one I can say something about with any trace of authority) towards the end of the pure silver-billon era, that confirms your proposition about coinage being on a silver standard. Charles IX (1560-1574) had deniers tournois (i.e., 1 d.t.) weighing 0.8 g and all the way via doubles, liards, douzains etc. up to testons with a value of 144 d.t. and weighing 9.6 g. The teston has 0.899 silver, the denier tournois 0.060. The silver content per d.t. of value is 0.060 g for the teston resp. 0.048 g for the denier, and it is pretty consistent around that figure for the whole denomination range. And as you say, to make the small denominations manageable and not become too tiny to handle, they had to have much lower silver fineness.

Charles IX's successor, Henry III, changed the game plan by introducing pure copper for the lowest denominations (1 and 2 d.t.). It was not his idea, copper coins had been in use in the Low Countries for decades.The copper 1 d.t. weighed 1.57 g, about twice as much as the former billon 1 d.t., which I think was a way to instill some trust in it - no silver, but at least it was heavier than the old coins. The copper 2 d.t. weighed exactly twice as much as the 1 d.t. (With copper being worth roughly 1/100th of silver, the 1 d.t. coin should have weighed about 4.8 g to follow a "copper standard", but that was not the intention.)

For Henry III there are five types of liards, grouped into two emissions. 1st emission, 1576-1577, has fineness 0.135 and weighs 0.956 g. 2nd emission, 1578+, has fineness 0.125 and weighs 1.003 g. 1st emission thus contains 0.129 g silver, 2nd 0.125 g.

Overall, silver content sank with time. The Charles IX coins I discussed contain on average ca 0.55 g silver/d.t. of value. Those of Louis XI, a century earlier, also show a consistent amount of silver/d.t. over the denomination range, but with 1.0 g silver/d.t.

I think I have a bunch of those dreipolkers too (don't recall if specifically this date though), plus similar contemporary issues from Prussia and Sweden. Numista doesn't give silver contents for any of them (IIRC) and I got the impression that they varied a lot (though were generally low) so it's possible that there's actually no way to assign official fineness to those.

I think I have a Prussian grosz from the 1530s as well, but I forgot if it was Ducal or not... and unlike the poltoraks I'm not confident that I have photos.
I do have pics of some 18th and 19th century German States coins whose fineness I couldn't find on Numista, and maybe I'll try to list those.

I'd be surprised if Christina's Livonian solidi could be assigned anything. It doesn't help that there's a bunch of contemporary counterfeits from Suceava, though AFAIK my coin (1645) had been declared to be probably from the original issue.

EDIT: I don't suppose you'd know how little silver there actually was in the Bohemian 1/4 (kipper) kreuzer from 1621-22... Krause says "silver" but the examples online (as well as my coin) all just look like copper, which suggests to me that most likely it was some kind of very low grade billon, but I couldn't find a reference to the exact silver content.

Gumowski has this at 0.375 (6/16ths)



Gumowski has the dreipolkers late in Sigismund III's reign also at 0.375 starting from 1623. However, the Elbing coins are occupation issues under Gustav Adolf of Sweden, and it's not to hard to imagine reasons the composition might have deviated from the official one.

That's all I can help with.

Here is what Gumowski has for the dreipolkers:
Munzkommission 1614 - 0.469 (7 1/2 / 16ths)
Munzkommission 1619 - 0.406 (6 1/2 / 16ths)
Munzkommission 1623 - 0.375 (6/16ths)
However, there is also this paper
https://www.ncbi.nlm.nih.gov/pmc/ar.../PMC9654620/
where the authors claim the actual silver contents are much higher, in the 60-90% range. They did not use XRF, but used other analytical techniques. I am a bit skeptical that these coins would have been struck at comparable or higher silver content than higher value coins.

My lowest type for this thread is this 2% double mite from the Duchy of Brabant struck under Philip the Good, 1434-1467:



Despite the low value of the coin, the diemaker took just as much time engraving Philip's complex coat of arms and the long legends, as on the higher value types.

I think we have these contributions for the 9% and lower range:

9% Lithuania 2 denars KM#15 (tdziemia)
.......Poland Gdansk solidus/Schilling N#96806 (tdziemia)
8% Cyprus (Venetian) carzia N#127028 (january1may)
7% France Francois I denier tournois (#39083 (erafjel)
6% * Poland 1 solidus/schilling Torun N#182131 (tdziemia), probable not confirmed
5% France Louis XI obol tournois N#65414 (erafjel)
.......Romean Empire, Diocletian antonianus (paralyse)
4% France/Hainaut 2 deniers #95706 (tdziemia)
3% County of Flanders 2 mites N#126945 (tdziemia)
2% Duchy of Brabant 2 mites N#108934 (tdziemia)