I spent an afternoon with Rand about 20 years ago, in his studio at his home in Connecticut, interviewing him about his IBM work, logos, graphic design and corporate identity. It was an interesting few hours, and as I recall, he showed me the presentation book he'd made for the Next logo (among other things).
Here's a little detail you might not realize about the IBM logo, although it won't surprise anyone who works in graphic design: there are two slightly different versions -- one for black or blue print on a white or light background, and another for 'reverse' use (white-on-black). The size and spacing of the bars is slightly different, and the fourth bar down in the M is one solid piece in the first version, but two separate pieces (breaking in the middle) in the reverse version.