I just stumbled on this artifact that sold at auction. I would have loved to have a shot at it, but who knows what it sold for. This harness pendent carries the same arraingment as the heater shield. Here is the description:
Rare Medieval 'Humphrey de Bohun, 4th Earl of Hereford and Essex' Heraldic Harness Pendant 024483
Copper-alloy with gilding, 10.90 grams, 33.45 mm. Circa 13th-14th century AD. A cast copper-alloy horse harness pendant with the remains of the transverse pierced lug attachment above. The pendant is in the form of a heater shield bearing the arms of Humphrey de Bohun, 4th Earl of Hereford and Essex (1276 – 16 March 1322) who was born at Pleshey Castle, Essex. Humphrey (VII) de Bohun succeeded his father as Earl of Hereford and Earl of Essex, Constable of England and the title of Bearer of the Swan Badge, a heraldic device passed down in the Bohun family. This device did not appear on their coat of arms but is featured on the personal seal. Humphrey was one of the leading military commanders of the day, taking part in Edward I's campaigns in Scotland, as well as many tournaments where he earnt a reputation for gallantry. Humphrey later became a bitter enemy of the king, promoting the reforms of the Ordinances. He was killed in battle at Boroughbridge, leading an advance across the bridge when one of the enemy pikemen thrust upwards and skewered him. Reference: Read, B. Metal Artefacts of Antiquity, vol.1, Langport, 2001 items 408-16. Very fine condition, gilding intact. Provenance: from an old English collection, found near Norham castle, Northumberland, guarding one of the key crossings of the River Tweed.
From:
http://www.time-lines.co.uk/medieval-humphrey-de-bohun-4th-earl-of-hereford-and-essex-heraldic-harness-pendant-024483-35606-0.html