5 Pounds - Elizabeth II The Infamous Prison, Silver Piedfort

This piedfort was issued as part of the Royal Mint's Great Engravers series, specifically commemorating the Tower of London — a fortress that functioned as a royal mint itself for roughly five centuries, from Edward I's recoinage of 1279 until operations transferred to a purpose-built facility on Tower Hill in 1812. The Tower Mint was notoriously difficult to manage: workers were paid partly in clippings, theft was endemic, and the cramped medieval buildings made systematic quality control nearly impossible.

Piedfort format — double the standard planchet thickness — originates in French mint practice, historically used to produce presentation pieces for assay verification.