I've just realized that the backup in which I found the OBJ that was missing from the original ShareCG upload also contained a slightly later version of this which had a spine that bends too. 

I've uploaded that to my HiveWire3D book stuff topic, post #53.

There's also a short video of the book opening on my Youtube channel Proof of principle - Poser ERC opening book - YouTube

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The 3Dcheapskate* occasionally posts sensible stuff. Usually by accident. And it usually uses Poser 11, with units set to inches. Except when it's using Poser 6 or PP2014, or when its units are set to PNU or something else.
*soon only to be available in two flavours -  DAZ and Renderosity