What are antique brooches usually made of?

Silver and gold dominate the titles, silver slightly ahead. Gold is nearly always given by fineness, with 9ct the most common, then 18ct and 15ct. Platinum is a small minority and keeps company with the diamond pieces. At the lower end of the range you'll find brass, chrome, pewter, silver-plate, bakelite and pinchbeck.

Which period do most of them come from?

Victorian and Edwardian are the two largest period groups, Victorian by a wide margin. Both labels cover long spans, and titles also use looser forms like 19th Century, mid Victorian and circa 1880. By decade, the 1950s is strongest, then the 1930s and 1920s. Georgian pieces are scarce, at 41 titles, so anything earlier than about 1800 rarely appears.

Why are so many brooches Norwegian?

Norway is the strongest single non-British origin in the archive, named in 100 titles, most of them silver. Danish silversmiths turn up in the sample too. The group is mainly silver and enamel work from the 1930s to 1960s, and the enamel butterfly is its signature form. Both maker names carried by three or more dealers are Norwegian.

What does a convertible brooch mean?

It's a piece fitted with both a pin and a loop or bale, so it can be worn as a brooch or hung as a pendant. Pendant is named alongside brooch in 144 titles. A further 108 titles say pin, covering stick pins, tie pins, kilt pins, jabot pins and hatpins, along with clip and double clip brooches.

Are stone weights given in the descriptions?

Only toward the upper end. Lower down, a title names the stone and stops there; carats start appearing as the pieces get more serious. The largest sampled figures are a 19.00 carat brilliant-and-baguette double brooch, a 17.89 carat yellow Ceylon sapphire and a 71.96 carat citrine.

How many come up for sale each year?

About 215 come to market in a year on Sellingantiques, from a body of roughly 1,500 listings. Ninety-eight dealers have listed them. That makes brooches one of the most widely stocked jewellery forms on the site.