Carlisle Castle was under siege from October 1644 through its surrender on June 25, 1645, but the mint itself only operated in May 1645 using silver plate collected from citizens. Only Shilling and Three Shilling denominations were minted with certainty, with estimates of ~3460 of the former and 1000 of the latter originally produced, with a few dozen of the shillings and a dozen to low teens of the three shillings surviving. Issues can read "OBS CARL" (obsidium → "siege").