The German Tiara was donated to Pope Leo XIII by Kaiser Wilhelm I of Germany in 1887, officially to commemorate the golden jubilee of Leo's ordination as a priest. However, it is suspected that its donation was an attempt by the German government to rebuild bridges with the Holy See following the kulturkampf campaign against Roman Catholicism that had been mounted by Chancellor Otto von Bismarck.
Contemporary media reports record that Pope Leo wore the tiara when being brought in state to St. Peter's Basilica for Easter ceremonies to show that the Holy See had reconciled with the German Empire.
It is not known if it was worn subsequently.
In 1903 the tiara was valued at $750,000.
References
German Tiara Wikipedia(Text) CC BY-SA