Cast-iron key for Alexander III's entrance to the fortress in Novogeorgievsk

This cast-iron key was for the entrance used by Alexander III at the Novogeorgievsk fortress (Modlin in Polish) and was brought back as a trophy in 1918 by Charles Léty, a Mosellan combatant in the German Army.
Constructed by French General Chasseloup-Laubat in 1807, the Novogeorgievsk fortress was located on the Vistula, upstream from Warsaw, at the confluence of the Narew, and was the forward-most Russian stronghold against Prussia. It is made up of two lines of detached forts and modern concrete forts. The Russian garrison, commanded by General Bobyr, includes the 58th, 63rd, 114th, and 119th divisions and four artillery brigades with approximately 1200 cannons.
After the declaration of war on August 1st, 1914, Germany and Russia clashed on Polish ground (Battles of Tannenberg and the Mazures Lakes, won by the Germans). As part of a vast offensive on the Eastern frontline in July 1915, the Group of Armies of General Von Gallwitz were tasked with pushing toward the Narew which, along with the Vistula and reinforced by the Novogeorgievsk fortifications, formed a significant obstacle. The role of commander-in-chief of the siege was entrusted to the same man who secured victory in Antwerp, General Von Beseler. At the beginning of August, Novogeorgievsk was surrounded. The Germans had high-caliber artillery pieces (420 mm and 305 mm in particular) to reinforce the infantry attack forces from August 13, 1915. Despite the Russians' resistance, which they maintained for six days, the German infantry infiltrated the forts. On August 19, the final cannon shot was fired from Novogeorgievsk. The next day, General Bobyr signed the surrender. Over 85,000 men were taken prisoner.