Onluk - Abdülmecid I Kostantiniyye mint

The onluk was part of the sweeping monetary overhaul launched under the Tanzimat reforms of 1839, the same administrative restructuring that reshaped Ottoman civil law, taxation, and military conscription in a single decree. Abdülmecid I, barely sixteen when he ascended, was pushing a modernized billon coinage into circulation while simultaneously negotiating the aftermath of the Near Eastern Crisis — Egypt's Mehmed Ali had just forced the Ottomans to the brink of territorial collapse.

The .170 fineness placed these coins at the lower edge of anything meaningfully silver, and they were treated accordingly by the public.