This is inside a book for a model set. You can buy the actual product here.
I wish I'd taken more screengrabs of the whole process, but I didn't. It started as an illustrator sketch. Rough pencil-tool lines quickly thrown down, with the straight lines of the pen tool, which is useful with something as exacting as redrawing a Lego model. I think I used the model as a base to sketch off of, to keep it exact, but I don't see it in the file.