Inscribed: “H.M.S. ‘Firefly’ destroying the magazines at Brandon, Gulf of Bothnia. This plate is respectfully dedicated to Capt. H.C. Otter, the Officers, and Crew of the Ship, by their obedient Servant, H G Cramer | Naval Assist.t Surveyor”.

The action – against a considerable shipbuilding centre in the port of Wasa (Vaasa, Finland) – took place on 8 August 1855. As described in W.L. Clowes, The Royal Navy: a history from the earliest times… (1897-1903), vol.VI, pp.490-1, Otter opened fire from 1,500 yards and had succeeded in setting on fire all magazines and storehouses by 2.30pm, before backing out under heavy fire shortly after 8pm, the conflagration being no longer in danger of extinction.