That isn't universal. There are places which have no stamping machines anymore. Because any ticket, be it bought at a ticket machine, or the driver, already is

That isn't universal. There are places which have no stamping machines anymore. Because any ticket, be it bought at a ticket machine, or the driver, already is "stamped". There may be some leftover installs in older vehicles, on lend from somewhere, or occassional use out of the "Verkehrsverbund", to be lended elsewhere, but they are getting rare. I actually can't remember when I've last seen them.