Voorwerp: Kruisboog Fibula.
Afmeting: 8x5 cm.
Periode: 0 tot 400 nchr.
Circa early 3rd-4th century AD
This is the most complex of the Roman brooches. In the early verions the terminals were more bulbous and part of the bow and wing. In the fourth century the knobs became very large with some being screwed on. A hinged pin ran through the top of the bow holding the top knob in place.
The bow and catchplate could be elaborately decorated with incised patterns - ring and dot, lines, chevrons and spirals. They ahve been found made from most materials from bronze to gold, or gilded bronze. Crossbow brooches were common on the continent, but tended to be hollow, unlike the solid Romano-British types.
QUESTION: How does it work?
Let's just say that it creates an electromagnectic field, that when passing over a metal object the circuitry knows that there is something there because of the conductivity of the object.