This is not mission critical or anything desperate like that. I am just curious.
I use that marvelous innovation, Soxy, from Rorohiko, as I have several versions of InDesign on my computer (iMac, OS 10.6.8) and frequently need to save files in a version that matches that of clients who have not upgraded. Soxy works beautifully and, after a document has been opened in a particular version, its desktop icon matches that version.
However, there is a strange anomaly with InDesign books (.indb files). If I open a book (which is basically a panel, rather than a document, of course) and then close it without doing anything, from there on it carries the appropriate desktop icon. If, however, I open one or more of the "chapters" of that book and do work on them, I need to Save the book before I can close it. When I do, the desktop icon goes back to the generic Soxy icon.
It seems that every time I save an .indb file, instead of just saving it, InDesign replaces the existing file with a completely new one. Is this so? Curious. I know this is probably a question I should address to Rorohiko, but I figured the gurus who inhabit InDesign Secrets pages would know the answer.