My guess is that they are simply different versions of ojdbc6.jar
(Oracle JDBC drivers compiled for Java 6). The file sizes on Oracle's site suggests that this may be the case (they are close).
I'm guessing someone was used to using the ojdbc14
/ojdbc15
jars and renamed the jar for consistency-sake?
I'm thinking your ojdbc6.jar
is the 11.2.0.3 version, and the ojdbc16.jar
is the 11.2.0.2.0 (close file sizes).
You should be able to confirm this by looking in the jars' manifest files (they should have the version information).