These wide buckles were common in Europe from the 15th century onwards. Many can be seen on baldrics or fastening the wide belts favored by Burgundian ladies.
Measurements: L= 1.7 cm, W= 5 cm, Strap-bar length= 3.6 cm Weight= 10g
A similar shape can be found at: https://finds.org.uk/database/artefacts/record/id/1006914
