King Abdulaziz (15 January 1876 – 9 November 1953) was the first monarch of Saudi Arabia, the third Saudi State. He was referred to for most of his career as Ibn Saud.

Beginning with the reconquest of his family's ancestral home city of Riyadh in 1902, he consolidated his control over the Najd in 1922, then conquered the Hijaz in 1925. Having conquered almost all of central Arabia, he united his dominions into the Kingdom of Saudi Arabia in 1932. As King, he presided over the discovery of petroleum in Saudi Arabia in 1938 and the beginning of large-scale oil exploitation after World War II. He was the father of many children having 45 sons, including all of the subsequent kings of Saudi Arabia. (Wikipedia)

My guess is that this was taken when Ibn Saud and 40 men advanced on Riyadh and took it from the Rashidis. This recapture marked the beginning of the Third Saudi State.