Bohun swan

The Bohun swan: A swan proper gorged (with or without a crown) and with a golden chain
Counter seal of Humphrey de Bohun, 4th Earl of Hereford (1276–1322), attached to the Barons' Letter, 1301, showing the Bohun swan above the escutcheon and supporting the guige strap

The Bohun swan, also known as the Bucks Swan, was a heraldic badge used originally in England by the mediaeval noble family of de Bohun, Earls of Hereford, and Earls of Essex.