As other responders have pointed out, the interest should be 2.5% x 1,000 Guilders, not 2.5% of the amount of gold that was in 1,000 Guilders in 1,648. Its wor

As other responders have pointed out, the interest should be 2.5% x 1,000 Guilders, not 2.5% of the amount of gold that was in 1,000 Guilders in 1,648. Its worth going through the math: 2.5% x 1,000 Guilders = 25 Guilders. The Netherlands replaced the Guilder with the Euro in 2002, with an exchange rate of 2.20371 Guilders per Euro. If we interpret the contact as being due in Euros, then the interest should be €11.34/year, or at today's exchange rate, $13.44/year.