English: Description: Two discs, one of silver and one of copper alloy (see analysis below). Both are of identical shape and size; c. 53mm in diameter and with a central hole of c. 20mm diameter. In the middle of the ring thus formed, the silver disc has lightly tooled grooves forming a ring of mushroom shapes, the stem of each mushroom standing on the previous one's cap. Each mushroom's cap has a short line linking it to an outer or inner frame, forming a row of almost T-shapes to either side of the mushrooms. The entire ring is 6.5mm wide.

The ring is interrupted by two circular matt grey areas, probably solder (see analysis below), also apparently outlined with lightly engraved lines. The outer edges of these circles coincide with the outer edge of the main ring of ornament, but their inner edges project a little from the ring. They are almost directly opposite each other, but not precisely; if one is at 12 o'clock, the other is at about half past six.

Also a little off 3 o'clock, perhaps at half past three, is an oval hole in the silver plate (c. 3 x 4mm) between the inner edge of the ring of mushroom shapes and the inner edge of the disc itself. This is presumably a pin hole; it is orientated with its long axis parallel to the edge of the ring, and is surrounded by an area of iron corrosion, presumably from a missing iron pin, which extends to the outer edge of the ring of mushroom shapes. On the inner edge opposite this hole is a notch with bent-up edges; although there is much damage in this area, the most complete part looks as if the edge is original and formed a stop for the pin.

There is a further lightly engraved line forming a border just inside the outer edge of the silver, about 0.7mm in from the edge. The silver is very thin, at minimum 0.2mm thick; it could well be described as a thick foil. The reverse is shiny, with much copper corrosion, and some of the deeper incised lines on the front can be seen on the reverse.

The copper-alloy ring of the same dimensions is now in several pieces. One face of this is shiny and silvery beneath the copper corrosion products; the other face has areas of matt grey which look like solder. This ring has a notch matching that in the silver plate, but without the bent-up edge; the notch measures c. 4 x 3mm and its long axis is perpendicular to the inner edge of the ring, which it cuts through. There is extensive damage to the copper-alloy ring in the area corresponding to the oval pin hole in the silver ring, so it is not possible to tell whether there was a matching hole here. The two discs were probably originally soldered together.

Dimensions: diameter 53.87 mm, width of band 16.63 mm, thickness of silver in less corroded areas 0.2mm. Both plates measure circa 0.9 mm in thickness including the corrosion. The silver element weighs 3.3g and the copper-alloy element weighs 6.3g, giving a total of 9.6g.

Analysis: Non-destructive X-ray fluorescence analysis (XRF) of the surface of the shiny upper plate indicated a silver content of approximately 92%, with at least 6% copper. XRF analysis of a shiny area on the surface of the lower plate, now covered in green corrosion products, indicated that the body metal of the brooch is a bronze alloy (copper and tin). Lead and copper were detected in high quantities in one of the two matt grey areas on the upper surface of the silver plate, and could indicate the presence of a soft solder.

Discussion and Date: The wide band of the brooch, and the hole, notch and stops for the pin, suggest that the object should be interpreted as a quoit brooch; the diameter:bandwidth ratio of 3.1 is well within the limit of less than 4.5 suggested by Ager (1990, 156 and fig. 1). The peculiar composite construction of the Stone brooch is, however, unparalleled among quoit brooches, and the 7th-century date of its ornament is also unusual; hitherto the only certain example of a 7th-century quoit brooch has been the garnet-set gilded silver example with relief Style II decoration from Castle Bytham, Lincs (Ager 1985, 22, no. 30). Barry Ager has, however, kindly drawn attention to another 7th-century jewelled quoit brooch, that from Barrington in Cambridgeshire, now in the Ashmolean (MacGregor and Bolick 1991, no. 10.18). This has solder marks to either side of the pin notch (not mentioned by MacGregor and Bolick) from missing soldered-on pin-stops, and four small cabochon garnet settings in gold wire collars, with stamped annulets on the silver frame between.

Ager has drawn attention to the similarity between the Castle Bytham brooch and keystone garnet and composite disc brooches (Ager 1985, 22; e.g. Avent 1975, nos. 127 and 177), and there are also broad similarities between the design of the Stone brooch and the design of these composite disc brooches. At first sight the design of the Stone brooch closely resembles a layout for the frontplate of a composite disc brooch, with cloisonné ring, large central setting and pair of peripheral circular settings, but in fact all of the 15 relatively complete composite disc brooches studied by Avent (1975, cat. nos. 169-183) differ from the Stone brooch in that there should be four, not two, peripheral settings, and the outer cloisonné ring should be next to the rim, interrupted by the outer part of the peripheral settings, not further in as on the Stone example. In addition, all of these brooches have gold frontplates, not silver; the Stone brooch has a central void rather than a central setting; and the engraved ornament cannot have been a preliminary layout for a cloisonné design but rather must have simply been intended to resemble one.

Despite this, the idea of composite construction (the silver frontplate presumably being soldered to a copper-alloy backplate, allowing a thinner and more economical silver element) is likely to have been derived from the composite disc brooches, which began to be made in the early years of the 7th century (Avent 1975, 62).

The frieze of mushroom-shaped cells can be paralleled, with slight differences, within the Staffordshire Hoard (e.g. StH104); the rectangular buckle from Sutton Hoo Mound 1 has friezes of half-mushrooms (Bruce-Mitford 1974, pl. 86b). Both of these objects should be dated to the 7th century, the latter to c. 600-c. 625.

Although the exact motif of mushroom shapes does not appear in the known corpus of composite brooches, both the ornament and the construction independently suggest a date for the Stone brooch in the first half of the 7th century AD.