A quick internet search suggests that it is a German government Treasury Bond from the Hyperinflation period of the Weimar Republic (June 1921 and January 1924, see https://en.wikipedia.org/wiki/Hyperinflation_in_the_Weimar_Republic).

As I understand it revaluation meant that the old Marks were convertable at a rate of 1 real billion (a real billion being 1,000,000,000,000) to 1. Thus the milliard (1,000,000,000) bond you have would have been worth 1/1000 of a DM after revaluation. And since the DM was converted to the Euro at about 2 to 1 in the unlikely event that the German government would give you money for it it would appear to be worth 1/2000th of a Euro, approximately.

But there might be a dealer value to it. I found an add for an "uncancelled certificate" which suggests it might be worth a couple of hundered USD to a dealer. See: http://scripophily.net/ziscdesdereg.html