This is a Roman enamelled copper-alloy strap fitting, believed to date to c.AD 100-300. It was found this past winter by metal-detectorist Dave Arveschoug near Middle Rasen in Lincolnshire.
Although most of its original edge has been worn away, the object largely retains its original disc shape. It is relatively small, measuring only 27mm in diameter, but it is intricately decorated. On the front of the fitting, in the centre, is a raised circular dome. In the middle of the dome is a slight depression, where it is believed a setting may once have been fitted, and radiating around it are a series of 21 short grooves.

The flatter, outer part of the brooch is decorated with a relief-moulded zig-zag line, creating 14 outward- and 14 inward-pointing triangles. Ten of the outward-pointing triangles are filled with dark blue enamel and, of the other four, a trace of the same coloured enamel can be found on one but it is mostly filled with an off-white material, which appears to be vitreous and hence may represent a (now degraded) initial layer of enamel. The other three also contain the same off-white material. The 14 inward-pointing triangles contain a brown substance, which is possibly the remnant of heavily degraded enamel.
On the reverse there is a circular depression, now filled with soil, which corresponds with the raised dome on the front. This is bridged by a cast-on loop that is rectangular in cross-section and which is severely worn and eroded.
For more information on this strap fitting, see https://finds.org.uk/database/artefacts/record/id/1023365 or search for NMS-787BFC on the PAS database.
The Portable Antiquities Scheme is an initiative, funded by the DCMS, to encourage the voluntary recording of archaeological objects found by members of the public in England and Wales. For more information on the Scheme, and to browse its database of over 1.5 million finds, visit www.finds.org.uk. Information for this find was provided by Andrew Williams, Historic Environmental Assistant (Finds) – Norfolk County Council.