Germans with statutory health insurance keep a small booklet for the dentist, the Bonusheft. At each yearly checkup the dentist stamps it. When a patient later needs dentures, the stamps are worth money. Without a bonus, the insurer pays a subsidy of 60 percent. After five years of stamps it pays 70 percent, after ten years 75 percent. What counts is ein Stempel pro Jahr, also ein lückenlos geführtes Bonusheft, one stamp per year, so a booklet kept without gaps.