I believe it is an 1841-1861 Gibraltar 2-quarts. @philologus_1’s post confirmed my initial suspicions. I thought, “Gibraltar!” the moment I saw that key in the design.
Thanks for playing, everyone! Winner winner chicken dinner! GIBRALTAR Time of Victoria, 1837-1901 CU 2 Quarts (28.0mm, 10.50g, 12h) Dated 1842/1. Royal mint, London, UK Obverse: VICTORIA D: G: BRITANNIAR: REGINA F: D: around “Young Head” portrait of Queen Victoria left, date below Reverse: Castle with three turrets; GIBRALTAR above, small key above TWO QUARTS. below References: Numista 17866 Mintage: 48,000 With its elevated position overlooking the narrow entrance/exit to the Mediterranean Sea, the peninsula of Gibraltar, on the southern coast of Spain, has long been recognized as an important strategic stronghold. The first permanent fortress on Gibraltar was built by the Almohad Sultan Abd al-Mu’Min in 1160, after the Islamic conquest of Iberia. Over the next several centuries, Gibraltar passed back and forth between various powers as they fought for control over the peninsula. The British acquired it in 1713 after the signing of the Treaty of Utrecht towards the end of the War of the Spanish Succession, and Gibraltar remains a territory of the United Kingdom to this day. The reverse of this coin depicts the famous “Castle and Key”, the coat of arms of Gibraltar which was granted by Spain’s Queen Isabella I in 1501. I'll take a look at what I've got later today and see about posting up another.