> [I also declare] to have awarded and given 75 Carolus guilders of twenty stivers apiece per year as heritable annuity, to be paid one half of the annuity aforesaid on the 9 th of June 1625 and the other half the 9th of December following and so on every six months until repayment with all payments entirely free of all taxes, impositions or burdens of whatever name or title none excepted.
It is confusingly written, but what it means by repayment in the above paragraph is not "until you get your 1200 guilders back in these 75-guilder installments", its meaning is clarified by the next paragraph,
> On such conditions that I or my successors [unreadable] of the aforesaid Leckendijck may, at any time when it pleases us, extinguish, repay, and buy back the said annuity in full at once and not in parts or fractions with the sum of one thousand two hundred Carolus guilders
which explains how the board can get itself out of this obligation: by paying the original principal of 1200 guilders back.
Curious why the board never paid back the original principal at any point in time over the past 400 years?
If the current annual interest of 2.5% cited in the article is €13.61, that would make 1200 guilders €544.40.
Did they just forget to? Did they figure the bond would eventually disappear? Or did they at some point think it was really cool to have a piece of "living history" and want to keep the world record alive for oldest active bond? If so... when?
It's such a low amount it's barely a blip on the budget of the successor issuer and by the time it was rediscovered in modern times it was enough of a historical novelty it was more interesting to keep it than to cancel it. Most of these bonds go years without being collected on.
A similar one owned by Yale can be viewed online [0]. It was issued in 1648, and it seems to have a fairly continuous payment history since then. There are gaps of a few decades, but nothing too extreme.
There's a pretty continuous line between the carolus guilder and the euro. For example, the modern-day (2002) guilder was fixed at an exchange rate of 2.2 GLD = 1 EUR. Previous coins also had a more-or-less fixed ratio, aided by the value of the gold and/or silver they were made out of.
If you want to treat it like a completely separate coin, you'd have to buy historical carolus guilders in auctions. They seem to be worth about €1500 [0], although the same amount of gold can be bought for only €240.
Currencies rarely "go away". They are usually replaced by new ones, and the government will buy the old currency and pay you in new currency. Imagine the mayhem if a government decided that all money everyone owned would suddenly be completely worthless!
It is confusingly written, but what it means by repayment in the above paragraph is not "until you get your 1200 guilders back in these 75-guilder installments", its meaning is clarified by the next paragraph,
> On such conditions that I or my successors [unreadable] of the aforesaid Leckendijck may, at any time when it pleases us, extinguish, repay, and buy back the said annuity in full at once and not in parts or fractions with the sum of one thousand two hundred Carolus guilders
which explains how the board can get itself out of this obligation: by paying the original principal of 1200 guilders back.