How to spend a lot of money on the wrong watch

If you have been buying watches for a while, there is probably one in a drawer that you wish you had looked at more carefully. There are three things worth checking every time, and you can check all of them before any money changes hands.

Start with the case. Every time a watch is polished, a thin layer of metal comes off, and a case that has been polished too often loses the sharp edges it left the factory with. Sotheby's describes the bevels going muddy or disappearing altogether. Look along the lugs. On a case that has been left alone, the angled edges are flat and crisp and catch the light in a clean line. On a tired one they have worn down into soft curves, the lugs look thinner than they should, and the whole watch looks slightly smaller and sadder than it did in the old catalogue. Compare the lugs with each other too, because a careless polish can leave one noticeably thinner than its neighbours.

While you have it in your hand, turn it over. Heavy polishing blurs the stamps on a case: the hallmarks on gold, and the reference and serial numbers on the caseback or between the lugs. If they are faint or missing, the polishing wheel has been there before you. And look at the finish. Plenty of cases left the factory brushed, with fine parallel lines, and an ordinary buffing wheel turns that into an all-over gloss. No watchmaker can put the metal back, so a polished case stays polished for good. A few honest scratches on a sharp case are much better news than a mirror shine on a soft one.

Then look at the dial, and before you reach for the loupe, look at the whole watch at arm's length. If the case is scuffed and the bracelet sags but the dial looks brand new, ask why. A redial is a dial that has been repainted or reprinted, usually to make a worn watch look fresh, and it costs money when you come to sell: all-original watches fetch more at auction.

Now get the loupe on the lettering, and look for letters that change shape or spacing within the same word, or numerals that don't quite line up with the track around them. A very glossy dial is another hint that it has been redone. Then compare the luminous paint on the dial with the paint on the hands. Old lume fades to cream or brown and barely glows in the dark, and the dial and hands should have aged together. If the dial glows a fresh white while the hands have gone the colour of weak tea, someone has been busy.

A refinished dial is acceptable on the right watch, as long as the work was done properly, the seller tells you about it and the price reflects it. Plenty of watches were given replacement dials when they went in for a service, and collectors argue about them endlessly.

Last, look hard at the seller. Photographs are taken in the best light the seller could find, on the best afternoon they had. Ask which parts of the watch are original and which are new. Ask for the service history: when it was last opened, by whom, and which parts were replaced. Ask what happens if it arrives running slow, or turns out not to suit you. Ask whether you can hold it before you pay for it. A seller who answers all of that clearly, and doesn't change the subject, is worth paying a little more to buy from.