Just for information (at the occasion of playing with
locking fonts of a book in this thread).
I noticed in the KindleUnpack of the sample AZW3, in the OPF
<!-- BEGIN INFORMATION ONLY section, the entry
<meta name="Unknown_(403)_(hex)" content="01" />
After removing this header, I found that the book opens with the ereader fonts instead of publisher fonts. I don't know which
<meta name=?> triggers Kindlegen to generate the 403 header, but I thought KindleUnpack could possibly improve its decode from
"Unknown_" to something like
"Open With Publisher Fonts".
To illustrate: