. . . is the absence of extraneous information offered by it's calendar display that employs apertures instead of pointers; the day, date, and month for any particular day are shown without any additional information. When comparing a G O perpetual with almost any other, the relaxed presentation of the calendar conveys only the information necessary for a perpetual calendars raison d'etre; with most other manufacture designs, the notable exception being U N, the analog pointer system shows the entire calendar on the dial. This may not be an obvious difference, and I will concede that others may not appreciate the difference, but to my way of thinking the clarity of the G O design is it's most compelling attribute. In technical terms, the aperture display is more demanding as the energy requirements are greater than with analog pointers; it's a testament to the skills of G O's designers that their perpetuals are as reliable and accurate as they are, a matter that I can personally attest to. Cordially, Art