Are these Russian samovars?

No. Samovar appears in more than half the titles, but the origins actually stated in this category are English or Dutch. The word travelled into the British trade and was applied loosely to urn-shaped tapped vessels. Not one eastern European example is named in the listings.

What are they usually made of?

Copper, in 41 of the 55 titles, frequently with brass mounts, taps and handles. Everything else turns up in ones and twos: pewter, bronze, bell metal, silver plate and japanned Pontypool ware. Sterling silver does not appear.

How old are antique tea urns?

The dated field runs from 1800 to 1920, with years clustering around 1800, 1880, 1860 and 1850. One Dutch pewter and bronze piece is described as circa 1750. Only 28 of the 55 listings carry a clean year. The rest are filed under labels such as 19th Century, Victorian or Georgian, which dealers use in place of a date.

Is a spirit kettle the same as a tea urn?

They did the same job by different means. The urn was a large tapped vessel holding hot water for repeated pots; the spirit kettle sat on a stand with a small burner underneath. Kettle appears in 16 titles and spirit kettle in eight, several of them reading "and stand" or "on a stand". Both are listed under this heading.

How often do they come up for sale?

Around seven pieces a year across the whole category on Sellingantiques, from seventeen different dealers over time. They arrive in ones and twos rather than runs.

Which ones sit at the top of the range?

The japanned Pontypool ware pair, the pewter urns and the Dutch kraantjeskan are the highest-priced sampled titles. Plain undecorated Victorian copper sits at the bottom. Within copper, large examples and those with original fittings sit higher than small or plain ones. The single 1920 piece, the latest dated, is among the least expensive.