"If it looks like an F, look carefully - it does not have a stroke across it"
The long s is subject to confusion with the lower case (or minuscule) f, sometimes even having an f-like nub at its middle, but on the left side only, in various roman typefaces and in blackletter.
"This appears in Gothic script, which gave way to a more legible script before 1450"
The long s fell out of use in roman and italic typefaces well before the middle of the 19th century. In Spain the change was mainly accomplished between the years 1760 and 1766; in France, the change occurred between 1782 and 1793; in Britain and the United States, between 1795 and 1810.
Despite its disappearance from printed works, in England the long s survived in handwriting into the 1860s.