The standard modern classical guitar scale is 650mm distance from nut to bridge. Some modern guitars are even 660mm scale, which was thought to improve volume and projection, but at the expense of playability. The scale length of early romantic guitars was typically shorter, 635 being perhaps the most common, but scale varies widely between 596-650, with most being 620-635mm. Staufer used 4 main string lengths, 640mm, 625mm, 607mm and 596mm. Virtually all Legnani style instruments by Viennese makers use either the 607 or 596mm scales, and Panormo around 630-635. Scale varied by maker, by country, and according to the original customer's hand size.
Surprisingly, the modern 650mm scale was a very common scale for French romantic guitars, but not for Spanish guitars. The body of French guitars is rather small, but the bridge is very low in the table, which gives a greater string scale and gives a characteristic sound for Paris or Mirecourt guitars. (From Francoise Sinier). Baroque guitars had similar construction, so it is not surprising to find early 19th century guitars with bridges toward the end. Also, Baroque guitars used typically 650 scale, so some early guitars were also 650. Some Baroque guitars were even longer, 660-670mm. Over time this was shortened, but by Torres' day, 650 had become the standard again.
