""saved" the accrued (past-due ?) interest charge"
Yes, exactly.
Many of these were structured as 0 coupon. The rentes, by example, were perpetual (!) and 0 coupon and callable by the French government as well as being sold only in very large tranches and with little secondary market except Treasury buy-backs. Far more a passive store of value than an active investment instrument.
The Dutch issues were far far more varied.

Please don't tell Digby, but my clients and partners are not exactly the "man in the street" either - and if a little credulous at times, they are also well-armed and prone to be very cross if ill-advised.