There are two ways in which the tubing for a flute can be produced, namely 'drawing' the tube or 'seaming' a tube.
'Drawing' a tube, the most often used method in modern times, is done by taking a flat disk of metal and 'drawing' or 'pulling' the material in to a tube shape using pressure.
A 'seamed' tube is produced by taking a flat piece of metal, wrapping it into a cylinder shape and then soldering the two edges together along the 'seam'.
In the 19th century the technology for making 'drawn' tubing was not advanced enough to produce metal for flutes and so the 'seaming' method was used. Many modern flute players feel that a seamed tube produces a different sound and so the technique is still employed today by some makers, although they are in the minority.
One of the possible problems with a seamed tube is that the seam can 'come undone' if the tube is damaged or expanded, such as in fitting a head joint, so if you are interested in a flute or head made with this technique please bear this in mind.