I know burning rubber arrive with the gx4000 and not have box. but is really true?
I found this old interview, and at the finish of page appear a picture of the burning rubber box?.
AmstradAction062-0007 (http://matt.lee.name/aa/AmstradAction062-0007.html)
Well, it's not uncommon for marketing departments in companies producing various samples and mock-ups as the products are going into production... This may have been a proof of concept, a guide for other companies or they maybe even wanted to provide a proper box and dropped the idea at a later stage.