Two stamps of Prussia, issued in 1866, are usually said to be on
gold-beater's skin. But they are really on a very thin tough paper which
has been treated with shellac, parrafine, or something which makes it
transparent, and afterwards coated with a gelatine preparation. On this
the design was printed reversed, i.e. only to be seen correctly when
viewed through the paper. The stamps were gummed on the printed side.
When they were affixed to an envelope any attempt to soak them off
resulted in the paper coming away while the design adhered to the
envelope, like a decalcomanie. Essays of this nature were made in a
number of countries, including our own, but Prussia was the only one to
make and use the stamps.

There are several varieties of paper which have threads of silk or other
fibre. The first of these is known as Dickinson paper, from the name of
its inventor. It has one or two threads of silk incorporated in the
paper in the course of manufacture. For stamped envelopes two threads
were generally used. They were placed about half an inch apart and the
envelope was usually so printed that the threads would cross the stamp.
For adhesive stamps only one thread was used. Great Britain and several
of the German States made extensive use of this paper. It has never been
successfully counterfeited. The best imitation was made by gumming
together two thin pieces of paper with a silk thread between them but
the fraud was not difficult to detect.

Some of the United States revenue stamps were printed on a paper which
had a few bits of silk fibre scattered through it. The paper called
granite or silurian has a quantity of colored threads mixed with the
pulp. In Switzerland blue and red threads were used, giving the paper a
slightly grayish tone. In Servia only red threads were used but in