Figure 1 of the US patent documentation, shows an isometric view of Microsoft's holder with the lid closed. A book (20) is shown inside the holder. The inventors envisioned the holder being made of a transparent material to "permit the contents of the older to be identified without requiring any external labels." The "double-acting" hinges (18) are also shown.
The inventors believed their design was an improvement on previous "holders," as it had better hinges and provided a stable support for open books even if they were "substantially shorter and narrow than the holder."
Image taken from U.S. Patent 4,588,074 - Digitized by Google