Nearly thirty-five years and no one noticed the damn thing. Took us until '81 to find out

Weather Station Kurt:
German automatic weather station erected by a U-boat crew in October 1943. After the war it was forgotten about until its rediscovery in 1977 and destroyed in 1981.

Nearly thirty-five years and no one noticed the damn thing. Took us until '81 to find out it was German.
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(TITLE FROM REDDIT r/HistoryMemes)