It is a Prussian veterans medal but for the "Enthullung des Posener Provinzial krieger denkmals" ( the unveiling of the Posen Province war memorial) dated 16 June 1888.
Both the Provence and the city of Posen, now in what is Poland, have had a turbulent past having swung between Swedish, Polish, Prussian , French, then Prussian again and finally Polish "ownership" again in a space of less than 250 years.
A Prussian state from 1772 until 1812 and then again 1816 -1918 it was the official home of Otto Von Bismark and a Duchy of Prussia , adding the title of Grand Duke of Posen to the list of Hohenzollern titles.
Like many Duchy’s it was required to create a Landwehr ( "Country soldiers") effectively a part time militia on standby in much the same way many countries have an Army Reserve nowadays.
Prussia relied heavily on its Landwehr regiments as they made up over 30 % of the Military and provided Landwehr Infantry, Uhlan and Artillery , ans later support units.
The Landwehr of Posen would have been active in the Franco Prussian war , not only that but they also put down two attempted revolutions in the province one in 1846 and a second in 1908.
German Monuments to war dead varied from a simple stone with a plaque or an inscription to a monument such as in Munich and I am not sure what form this monument would have taken
I cannot find any information specific to a Monument to Landwehr dead in Posen that is still standing, it would seem most German war monuments in the province have been torn down and monuments to the events of WW2 that heavily impacted the population of the province have since been installed. Posen Krieger denkmal.png Posen Krieger denkmal rev.png