An old cannonball on the "Altes Zollhaus" (Old customhouse) restaurant at the Friedberger Landstraße near Frankfurt Seckbach.
The sign reads:
"...this cannon ball is from the battle of Bergen in the "Seven years war" on April 13th 1795 between Prussia and France.
Victor was the french Marshall Count of Broglie who won against Generalfieldmarshal Prince of Brunswick-Wolfenbüttel."
There is a mistake here. 1795 was definitively not the seven years war, which was from 1756 to 1763, but the "War of the first Coalition" 1792 to 1797. That would make sense as there were several battles in this war in the Frankfurt area and Frankfurt was even occupied by the French in that war.