The Graffiti Printer by Ariel Schlesinger…. think Epson for the streets (though the demos and pics are all indoors). The website features a few images and a video. And there is an ironic mission statement that parodies the One Laptop Per Child campaign. I like the punch card style stencils- less practical and more whimsical. The whole thing looks kind of steampunk- like a prop from City of Lost Children. Schlesinger also has a number of interesting pieces at Dvir Gallery though none so print-related as the Graffiti Printer.
