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 try to bear this in mind.