In the upcoming Heritage Auctions Europe, former MPO, Auction 48 (November 26, 2015), a rare undated Gronsveld ducat will be available for bidding (Lot 710). Starting price is 4,000 EUR.
A copy offered for sale was sold previously in Laurens Schulman auction 26 (November 19, 2001) for 9,000 Dutch guilders, means about 3,591 USD.
The recent sale of this type was in November 2000 in Sotheby’s London Auction 571, Lot 627 (coin sold for 3,520 GBP = 5,849 EUR = $5,012, incl. Buyer’s Premium fee). Next to Joh. W. Stephanik copy, sold in 1907 by Frederik Muller & Cie, Sotheby’s ducat was the finest known of this type.
Ducats of this type were minted under reign of Joost (aka Judocus) Maximiliaan van Bronckhorst (1617-1662). This date is known in two types: with a large date and with a small date. Both varieties are described in detail in the Jasek’s book.
You may bid this coin here.