You will never find a Community Edition version with three digits, e.g. 5.2.1. This version scheme is exclusively used for Enterprise Edition releases. Community Edition 5.2 has had multiple GA releases, but each version will always state that it is "5.2.0" even if there are differences between those Community releases. Technically, the versions can be distinguished by the Maven artifact version, which is two digits and a letter, i.e. 5.2.g, or the GA version label that Marco has mentioned.
Of course versioning has changed in 6.0 - since then there has typically only been one GA per main release, and the Maven artifact version will actually be a three-digit number with the "-ga" suffix. At runtime though, it should still just state to be 6.0.0.
(Alfresco versioning schemes are hard and confusing to everyone)
