Beautiful sundial with string gnomon and alphabetical list of cities from Amsterdam to Zeitz, with American cities of the period included. The sundial gains its name, Diptych, from the two hinged leaves that open like a book. Portable sundials are mostly elevation sundials, with which the elevation angle of the sun is measured and is indicated after evaluation with the as known necessary declination, respectively the year date of the sun as time. As a rule, you also need to know whether it is morning or afternoon, because a certain elevation angle can be measured twice a day. Whoever owned this diptych, had knowledge about latitude and other factors of geographic orientation. Polychrome decorated papered hardwood with wire hardware and brass tacks. Washington is listed, so I think it is safe to say this piece is late 18th century, European. All paper surfaces are in very good condition with the interior panels being brighter than the exterior one. Circular wear line around the hinge latch. The compass works, although it is not completely accurate. In inches, 2, 5/8th long by 1, 5/8th wide, when closed it is ½ inch.