This selection of Belleek comprises a pair of Aberdeen vases, a small forget-menot trinket box, a pair of flowered spill vases, a pair of flowered menu holders and a flowered boudoir candlestick

A selection of Belleek baskets sold in London last summer which include an elaborate Rathmore basket (top centre), three covered baskets and a Henshall basket (bottom right)

Belleek porcelain is "a world apart" in its individual style and it has a "dedicated band of collectors", according to Mr Fergus Gambon, a ceramics specialist at Phillips auction house in London.

To understand what Belleek is worth, the most important factor is to be able to date it. Manufacturing is divided into periods, the earliest and most collectable being 1863 to 1890.

Mr Gambon said: "If it's not marked, it's not Belleek. Look for a mark that says `Belleek' or `Belleek Co Fermanagh'. If it says `Ireland' then it's the second period or later."

He says that pieces from the first period go for twice that of later pieces. For instance a basket from the first period might fetch £1,400, while a similar piece from the second period could go for £700. "As the periods increase the prices are lower," he says. Nevertheless more complicated modern pieces can fetch £400 to £500.

He explains that the colour of the stamp changes with the periods. The marks of the first, second (1891 to 1926) and third (1926 to 1946) periods are almost all black. The fourth (1946 to 1955), fifth (1955 to 1965) and sixth (1965 to March 31st, 1980) period marks are green while the seventh period (April 1st, 1980-December 22nd 1992) mark is pale yellow.

Another way of dating a Belleek basket is by looking at the base. During the first and for most of the second period, three strands of clay were used to weave the basket base. But by 1920 the factory used four strands to weave the base.

Mr Gambon says that some of the most amazing pieces are the baskets. These are made by laying thin strands of clay into a mould: "It's like weaving. The strands are woven while wet and the supporting mould removed. The rims, feet and handles are then applied."

All shapes of baskets have their own name, for example the Rathmore oval basket. It comes in various sizes. Supported on stem feet which look like the prickly stems of a plant the rim is decorated with porcelain ribbons. A profusion of flowers is applied around the basket side.

He says that a first period Rathmore basket in good condition would probably fetch about £2,000 in the larger size: that is some 28cm wide or just less than a foot.

There are dozens of other basket shapes and names. For example, the Henshall basket is the only one with an overhead handle most Belleek baskets have two handles, one on either side. The terminals of the handles are encrusted with flowers. A first period Henshall basket in good condition should fetch £800.

There are also covered baskets, that is baskets with a separate cover or lid. A fragile deep ovalshaped basket with flowers applied to the rim and sometimes all over the cover as well can fetch £1,400 to £1,500. These come in two sizes and the larger version from the first period could probably fetch £2,000, said Mr Gambon.

Other Belleek items include menu holders, candlesticks, decorative ewers (a jug not designed for use) and spill vases (vases for the mantlepiece from which a spill or large match was plucked to light the fire). There is also a wide range of teawares.

Belleek's speciality is to employ naturalistic forms like shells and other shapes related to the sea. For instance, a cup could be shaped like a shell upturned and the handle modelled to look like a piece of coral.

Mr Gambon says that teawares are less expensive and that any damage and even the teawares are fragile - has an effect on their commercial value. A fine first period teapot and cover could fetch £400 to £500, while cups and saucers from the first period could fetch between £100 and £200 each.