I borrow a sentence from rainisto's answer to point out the version and the variant numbers:
40.2012.21-3 is the firmware version. In particular this is the so-called PR1.3 release.
001 is the number of the variant. As rainisto wrote, this one (001) is the basic variant, or vanilla file, or the 'Rest-of-World' variant.
If the device previously had any different variant than 001, e.g. 009 for Central Europe, or e.g. some of the 3xx used for operator-specific variants, it is not possible to flash the device using a variant 001, because it would be considered a 'downgrade'.