PS: I should have added that, if you are interested in attempting a project such as this, and prefer black keytops with white characters to my silver card and black type, be advised to use a sans serif typeface, as the serifs tend to disappear when using this "reverse" style of typesetting, nullifying the effect of the font and making it just that little bit harder to read. Also, perhaps you might bear in mind - and I believe this has been scientifically proven - that black type on a yellow background is the easiest type to read.
PPS: Some traditionalists will, of course, say, "Don't do it!". But that's not always practical advice - except, naturally, for a machine of much greater significance. Perfectionists will spot the odd little bleamish on my job, but my excuse was that it was done in a huge rush for the Melbourne typewriter festival. The many people down there who used the Royal had no problems typing with it!