LONDON – How did the lantern clock get its name? Well, you only have to look at its crude but functional design to see the similarity. The four-square case housing the movement has opening side panels just like those in early candle-powered lamps.

The simple brass clock was just as popular as lanterns, but considerably more expensive. Introduced in about 1600, it was once the only type of domestic domestic timepiece available. There are other theories, though. One explanation might be that brass was once called “latten.”

They also go by the name of Cromwellian clocks, because the only clocks made in Oliver Cromwell’s time were lantern clocks, but the term is misleading. They were made long after his death in 1658. Others know them as bedpost clocks, presumably not because that’s once place where they could be hung, but more likely because of the four posts that hold the movement in place.

Whatever you choose to call them, they are perhaps the easiest clocks to recognize. All have a bell on top surrounded by a fretwork gallery, a weight to make the thing tick and chime and a short bob pendulum.

Sadly, however, because they have been around so long, most have been the target for all sorts of “restoration” over the centuries. The most dramatic is replacement of the original works with a spring-driven movement, turning what was intended as a pendulum-driven wall clock into a table or mantel clock.

Purists reckon such intervention, usually to reduce the number of times the clock needed winding, or perhaps to make it a more accurate timekeeper, is the clock’s ruination. Other less finicky collectors would regard this as part of the clock’s history and accept it as inevitable.

We were lucky when we acquired ours. Pooh-poohed as a fake by the huddle of dealers at our local Saturday village hall auction 40-odd years ago, we were convinced it was right and bought it for £100.

In those cavalier days when we were still learning about antiques, such a mistake would have been less upsetting than it might be today. Now part of our pension fund, we reckon we could add at least another zero to its value.

Lantern clock production lasted barely 150 years and being made entirely by hand, they were thus expensive. Robust but inherently crude in their manufacture, the earliest examples had a balance wheel or sometimes verge escapement that needed winding a least every 12 hours and sometimes every eight.

So the first thing that happened was that movements were replaced with anchor escapements capable of running for 30 hours. Both this and the original movements were driven by weights: one to power the going train (to make it tick) the other the striking train. When the eight-day duration spring balance movement was developed, clocks were updated again and the weights discarded.

Some lantern clocks, such as our own, were fitted with an alarm mechanism visible on the center of the dial and most, but not all, did not chime the hour. However, as a clock was passed down through the generations of a family, requirements changed and often the alarm mechanism was discarded and sometimes ham-handed attempts were made to modify the movement to either make it chime or stop it altogether if the strike was too loud – never good for an uninterrupted night’s sleep.

Almost all genuine lantern clocks have just one hand, indicating the hours, half hours and quarters – in other words making the clock accurate up to 15 minutes either way. So, in another modification, clockmakers were asked to add the necessary mechanism to allow the movement to run two hands and thus give greater precision.

However, these modifications are not common. Instead, the two-handed lantern clock is likely to be a modern reproduction, Smith’s making a particularly attractive example in the 1940s.

It’s amazing to consider that a clock made 350 years ago is still capable of running today. This was made possible in part by the addition of brass doors to either side of the clock movement. These were originally intended to keep out the dust, of which there was a great deal when even the best homes used straw on the floors.

The doors pivot on two lugs in holes in the top and bottom plate of the clock but easily come unhinged and over time often become lost. So, many clocks coming onto the market today have either lost one or both doors or else have had them replaced.

It is often difficult to tell the difference. Attitudes differ on whether this affects value and is really down to personal choice, but the purist would be disappointed by modern replacements.

The most attractive features of a lantern clock are the pierced decorative fretwork panels that sit on the front and sides of the case in the space between the bell and the dial.

These give the clock its character and are decorated with such motifs as a lion and a unicorn holding a shield; sea serpents; Latin inscriptions and stylized flowers and foliage. They are also often the area chosen by the maker to inscribe his name and place of origin.

They too are held in place by lugs, and lost frets are all too common. Similarly, fashions change and over the passage of time, owners will either have discarded the frets or replaced them with new, more stylish examples.

Although it is difficult to tell the difference, old replacements are considered more acceptable than new ones, and a clock with no frets looks distinctly odd. Modern replacements can be obtained but whether such a clock should be purchased in the first place is again a matter of personal taste.

Interestingly, perhaps through scarcity, altered clocks that 20 years ago might have been scorned by collectors and sold cheaply are now increasingly becoming accepted. A clock by an important maker is still a rare and important relic, even though it might have been altered over time.

The key is not to be fooled into overpaying for something that purports to be original but actually is not.

By CHRISTOPHER PROUDLOVE