Just to share with you this little gem that I got from eBay, a 1850 Swiss cover franked with a Zürich 6 postage stamp.
The Zürich 4 and 6 was first put on sale 1 March 1843, making it the second type of stamp in the world, after the UK's Penny Black three years earlier. The issue consisted of two imperforate stamps printed separately, each in five types, in sheets of 100, one with a large numeral "4" and the other with a "6", both inscribed "Zürich" at the top. The 4-rappen stamp was also inscribed "LOCAL-TAXE" at the bottom, since it was intended to pay for letters mailed within a city, while the 6-rappen, inscribed "CANTONAL-TAXE", was for use with letters going anywhere in the canton. The design was lithographed in black by Orell, Fuessli, and Company, with a pattern of fine red lines underneath, to discourage counterfeiting. Initially the red line were horizontal, but starting in 1846 they were printed vertically. These stamps were popular from the start, but were not printed in large numbers and are quite scarce today.