Final answer:
Maharaja Ranjit Singh wore the Koh-i-noor Diamond on his arm, a gem which became part of the British Crown Jewels in the mid-19th century.
Step-by-step explanation:
The diamond that Maharaja Ranjit Singh wore on his arm was the Koh-i-noor Diamond. This diamond has a long history, originally found in India's Golconda mines. The Koh-i-noor, which means "Mountain of Light" in Persian, was once the largest known diamond in the world and has been part of the Crown Jewels of the United Kingdom since the British annexation of the Punjab in 1849 after the Second Anglo-Sikh War. The diamond that Maharaja Ranjit Singh wore on his arm was the Koh-i-noor Diamond. It was one of the most famous diamonds in the world and is known for its size and historical significance.