I've never seen one of these before. https://www.ebay.de/itm/Original-Dr-Ruter-Sonnenuhr-Berlin-1946-Kompass-Uhr/382722122995
Once you push a button, the dial plate with gnomon seems to rotate by compass so as to align with magnetic north showing both summer time and winter time. I guess small adjustments are also possible (therefore the + and - markings). Dan Uza
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