./usr/java/lib/sunrsasign.jar in META_INF/MANIFEST.MF
Created-By: 1.3.1_19 (Sun Microsystems Inc.)
./opt/amazon/ebook/booklet/MobiReader.jar in META_INF/MANIFEST.MF
Ant-Version: Apache Ant 1.7.0
Created-By: Blackdown-1.4.2-02 (Blackdown Java-Linux Team)
I.E: Mixed version code is "factory stock".
I suppose one could script a look-up of all the *.jar files and "vote" on which answer is correct, or ;
Use the version known to work (1.4).