You might not think to look twice at Bob Webb on the street, but for nearly 50 years people have been paying to look at him — naked.

Art schools and creative industry professionals, including Academy of Art University and Pixar Animation Studios, now routinely hire the 67-year-old to pose fully nude. But when Webb began modeling in his home state of Oklahoma in the late 1960s, nude male models were expected to wear G-strings. “Culturally, we’re just more comfortable with female nudity — and there’s that old penis thing, ‘Whoa, that’s scary stuff,’” Webb says.

Watch Webb in action at a recent City College of San Francisco session, and find out what’s kept him modeling for generations of art students and professionals.