This was mainly a design experiment that I did while working in the summer of 2000 with Ken Birdwell at Valve Software. because I was so inspired by their wonderful "old beaten-up futurism" look.
All shading and texturing is being done procedurally at render time, in Java. The texture is my 3D noise function, computed in real time from the X,Y,Z coordinates at the surface, and added to the normal.
The directional lighting brings out the derivative of the noise function; the variation in shape and patina is based on the value of the noise function.