Some examples of early Swiss stamps where before 1908 the paper was gummed after printing and later on the paper was supplied already gummed!
The pre-1908 paper has the coloured fibers in a predominantly horizontal position - parallel to the direction of paper!
After 1908 we see the turn of 90 degrees!
The result was that the watermark Swiss Cross changed from vertical into horizontal [the watermark being an orthogonal watermark] and this had not been noticed by the Swiss philatelists until 2002!
I was familiar with this change already in 1975 but did only publish it in our national philatelic magazine in 1993! Still light years ahead of the Swiss!
As these stamps had been issued way before 1938 the wire structure is symmetrical!
to be continued ...