Magic lanterns, early forms of slide projectors used for entertaining children and adults particularly from the 19th century, can be worth hundreds or even thousands of pounds.

According to Mr Peter Bateman of Edward Butler Antiques on Bachelor's Walk in Dublin: "They're much more a British thing than an Irish thing. They would have been a real rarity in Ireland. Most of the slides you get are British based. They're mostly colonial."

Mr Michael Pritchard, camera specialist at Christie's in London, says magic lantern shows must have been very, very popular and magical events in the 1860s and 1870s. "You get stories of people being given ghost shows, covering their heads in fear and everything because it was so realistic."

Even today, he says, some lanternists give traditional lantern shows and they can still give you a great buzz. When it comes to estimating values, "the things to look for are anything that makes them slightly unusual".

For instance, an 1890s German magic lantern in the shape of the Eiffel Tower at a Christie's auction on November 25th is expected to fetch £4,000 to £6,000 sterling (€6,235-€9,353).

Another unusual item is a Planck clockwork lantern. "This is one of the oddities. It's one of those things that make it unusual. It makes use of clockwork to drive the slides through the aperture, so instead of having to push it through with your fingers a little clockwork mechanism actually feeds it through at a steady pace." (Estimate: £400£600 sterling.)

Cylindrical lanterns (tubeshaped instead of the more usual rectangular box) with a chimney on top and a hole for the spirit burner and the lens at one end can be valuable, with estimates from £600 sterling in the forthcoming auction. Mahogany magic lanterns from the 1870s have estimates from £150. The first magic lantern dates from 1649 but Mr Pritchard isn't sure if any of this vintage have survived. Most magic lanterns that turn up at auctions date from the 1820s through to about 1910, he says.

Most of them tend to be worth "somewhere around about £100 to £200. Then as soon as you get something exceptional like the Eiffel Tower, for example, they can go up to several hundreds or thousands of pounds.

"The most we've ever got for a lantern is £30,000. That was for a triunial lantern - like three magic lanterns on top of each other. We sold that in 1996. That was a world record price for a lantern," says Mr Pritchard.

It was extremely impressive, of very good quality, dating from about 1870 and made by one of the best makers there was, he says.

A French-made magic lantern, a Lampadorama, circa 1882 with painted Japanese scenes on the outside, is estimated at £600£900.

A double lantern comprises two magic lanterns side-by-side, while a biunial lantern is one lantern with two projection lenses mounted vertically. The biunials tend to be more valuable than double lanterns, with estimates for the biunials in the forthcoming sale from £800 and double lanterns from £400£600.

These allowed lanternists to project two slides at once, so you could get all sorts of special effects and dissolves between slides, he says. "Basically, you could do all the effects that you could do with a modern slide projector, except in a manual way."

Several miniature and collapsible lanterns from 1900-1910 are estimated at £400 each.

Finally, some of the slides can be more valuable than the lanterns. "The most we've ever got for a single slide is about £3,000. That was for a hand-cranked slide with lots of gears and mechanisms to show the movement of planets around the sun."

Joe Armstrong is at jmarms@irish-times.ie