I have a few books on the subject and you can go back to the 30's and find it. Most were Hobo Tags and there were a few fellows who were famous for their marks. (chaulk generally) I did that on a 28,000 a few years ago...looks like a cowboy hat with a swoosh on it. You can go back to the 60's and find a lot of art on subways in NY and on freight cars in the area. The pretty stuff I like and practice is definatly a 2000+ phenom.
Joe
