Many years ago (2004, actually), I struck up an acquaintance with Myles Walker. Myles had sold his SF to Tom Gerrard (pix here), and Myles still had some of his collected material, including a Ross Roy book. I bought the book, and never paid much attention to some additional ephemera at the back... Until just yesterday. It caught my eye, because a brochure for Spring Colors included some codes that looked a lot like the ones Matthew has been collecting and researching, that are printed on the build cards.
