Kronenthalers

The specific assay 873 fine is most likely a very simple fraction in terms of whatever unit was used as the standard of measure when the coin was made. The mint obviously did not use a decimal system of purity. That is just a modern standard equivalent.

My background is in Spanish American silver which for a long time used 903 fine as the standard. But the real measurement was actually 10 Dineros 20 Granos in their terms. In the Spanish system pure silver is 12 Dineros and each Dinero contained 24 Granos. Stated in decimal terms each Dinero represents 1/12 of 100% or 8.333333333...%. Each Granos represents 1/24 of 8.33333333 or 0.34722222222%

If you do the math that works out to about 0.9027 fine.

The alloy was therefore ten and 20/24 dineros of "pure" silver mixed with 1 and 4/24 dineros of copper. Keep in mind Spain was on an eighths base accounting system.

So Spanish silver used a measurement stated in terms that were unrelated to the decimal system. This is the case for most of these odd decimals.

It has absolutely nothing to do with the purity of silver coming out of any mine.

The next two questions you ask can be treated at once:




Weight measurement itself was not a problem by 1796 most mints had scales that could weigh metals very accurately. Several museums house great examples of scales used ca. 1800 and they were accurate to 1/1000th of a gram.

The second problem you hit on is that silver refining techniques were still "relatively" crude by present standards. By this I do not mean plus or minus 5% - that is horrible. I mean about 1% at the very worst. The method normally employed up to the 1550s was fire refining (cuppelation) which is based on the principle that precious metals do not oxidize when heated. The other metals in the ore melt combine with oxygen and form slag the precious metals remain behind. The yield can be 99% pure or better but the silver will contain gold and platinum as well as other minor impurities.

The Patio process developed in 1550 used silver amalganation to extract more silver out of lower grade ores. The ore was crushed and mixed with mercury. Precious metals amalgamate with the mercury and can be separated. The resulting bars are then smelted. So in the colonial era silver could be purified to 99% and was often weight checked by Specific Gravity. The traces of gold and platinum increased the SG and often accounted for the range of SG provided in period handbooks.

The next step occurred about 1870 when the cyanide leaching techniques were added. This lowered the gold and platinum content of silver. Other refinement brought silver purity to 99.9% in this time period.

The history of silver refining had been stable from Roman times until the early 1800s when 99% was normal with gold and platinum making up the rest. But between 1800 and 1970 purity standards and the ability to separate silver from all other metals went from 99.0 to 99.999 pure.

This is an interesting topic and forms part of the base theory that allows XRF testing to assist with dating old silver.

Actually mercury amalgamation is still being used. The toxic effects can be monitored and controlled. Cyanide leaching beds are also still used although the impact is more environmental.

Personally - I like that picture it gives the coin character. Something all MS coins lack terribly.

Perhaps that is why I find so much of interest in counterfeits and old worn originals - they are the working man's coins.

Exactly. There is however even more to it:
Kronenthalers were legal tender within the Austrian Empire till 1857. When Austria lost the Austrian Netherlands to France, the currency change only affected these regions.

Older Kronenthalers (from Franz I and Maria Theresia) were highly spread in all regions. Hence, even of a 200K mintage, many were likely to survive. This was not the case with the 1794 Kronenthaler minted in Brussels: not many of those had left the Austrian Netherlands and a comparatively large fraction was melted and changed over for francs. This makes that particular coin much less common than suggested by its mintage number.

Doing a little math on the precious metal contents, a colonial 8R would contain about .25g of Au/Pt. So if you find one in the silver scrap heap sold by weight for $20 for the silver, you're getting another $10 worth of Au/Pt thrown in for free.

It's just a feel-good factor swamperbob. An Au/Pt "billon" sounds good, even if you couldn't economically recover the metals. It's been a while since I've seen a shiny wrecked 8R in the scrap box, but it has happened. My most recent find that would qualify was a well-worn Napoleon I 5F ca 1800 for $19.95.

Gwyde --We are using the Pt/Au ratio as a de facto proof of a genuine coin made before 1830.

Our hope is that anyone trying to match an alloy from antiquity would find it hard because of contaminants now found in 999 silver and especially in commercial grades of copper. Even using melt coins is a problem because the minute traces of mercury and iron present would be difficult to introduce without adding other contaminants that do NOT belong.

The forgers would have to start with nearly PURE elemental metal, at least of a 999.999 fine standard to replicate the contamination levels accurately. Possible perhaps, BUT prohibitively expensive in practice. So for "normal" coins under $10K range the XRF tests seem definitive - so far.

[quote]Does anyone know about the edge inscription on these kronenthalers?[/quote

For Leopold II, the Kronenthaler of Miland 1792, edge inscription is PIETATE CONCORDIA. I don't know what it means and is it Italian?