167r: note in PW18 protocol about “K” as an abbreviation on 167r: is this "K" actually on 167r, somewhere else, or nowhere?
Case-sensitive oxygen search for "K" – 2 instances
**<id>p086v_1</id>** <head>Sable excellent pour <m>plomb</m>,<lb/> <m>estain</m>, et <m>cuivre</m></head> [...] Je y gectay deulx foys<lb/> <m>cuivre</m> allié de <m>☾</m> co<exp>mm</exp>e <m>vieulx K</m>.
**id>p147v_1</id>**
<head><mark>+</mark> Gect de <m>cuivre</m> allié de <m>☾</m><lb/> qui est co<exp>mm</exp>e <m>soubdure fort basse</m> <mark>/</mark> ard <ill/><comment>c147v01</comment><lb/> et <m>vieulx K</m> et quelque R<ill/><comment>c147v01</comment> sur xii</head>
In both cases, "vieulx K" is associated with a silver-copper alloy. This is typical of a billon alloy, so perhaps K could refer to a coin? The medieval écu had the initial K for Karolus (Charles VI), but it was made of gold and I think no longer in circulation in 1580s.
The German Kreuzer was abbreviated K and made of a silver-copper alloy in C16 (from C17 it was mostly made from copper alone).
See Wikipedia