Belgium

Gold weight and purity converter →
Rubens’ Altarpiece Contract with Personal Involvement Clause c.1619–1626
Peter Paul Rubens contracted for the Assumption of the Virgin altarpiece for Antwerp Cathedral at approximately 1,500 Flemish guilders, with the contract specifying that principal figures were to be executed “by his own hand” — a premium pricing tier that distinguished his personal work from studio-assisted production. Rubens operated what was essentially a creative production company in Antwerp, with documented price differentials for varying levels of his personal involvement, making his contracts among the earliest known examples of authorship as a quantified commercial variable. The Flemish guilder was a silver-based currency; the gold equivalent is estimated from the prevailing exchange with the Venetian ducat.
~1,425g
Muller, Jeffrey M. Rubens: The Artist as Collector. (Princeton University Press, 1989); Antwerp Cathedral chapter records cited in Vlieghe, Hans. Rubens Portraits of Identified Sitters. (Harvey Miller, 1987).
Brussels Master Weaver’s Fee for an Export Tapestry Commission c.1640–1690
Brussels dominated the European luxury tapestry trade throughout the seventeenth century, with workshops of the Raes, Leyniers, and van den Hecke families executing commissions for courts across the continent. Master weavers on major figurative series received per-aune (linear metre) rates that aggregated to 800 guilders or more for a substantial panel set, with quality clauses specifying thread counts, dye standards, and cartouche design written into export contracts. The Flemish guilder was a silver-based currency comparable in weight to the Dutch guilder; the gold equivalent is estimated at approximately 0.95g fine gold per guilder from the prevailing exchange ratios. This entry uses 800 guilders as a representative figure for a single-panel export commission.
~760g
Delmarcel, Guy. Flemish Tapestry. (Thames and Hudson, 1999); Brussels, Archives de la Ville, guild and trade records cited in Campbell, Thomas. Tapestry in the Baroque. (Metropolitan Museum of Art, 2007).