This is version 1.5.2.

If only bugs are fixed between releases, the "micro" version number
will change. For example, 1.2.3 will become 1.2.4. You should have
little trouble moving forwards or backwards (unless, of course, you
depend on the bug fix which means you won't be able to move
backwards).

If a new feature is added (new control, class, property, or method), 
The "minor" version number will change. 1.2.3 will become 1.3.0. This means
that you should be able to move forwards but might not be able to move
backwards (because you might be using the new feature).

If compatibility is broken (remove a feature, class, property, or method
or change the signature of an existing property or method), the "major" 
version number. 1.2.3 will become 2.0.0. This means you
might not be able to move either forwards or backwards.

