available at www.guerillasoft.com/EncSpot
EncSpot is, to the best of my knowledge, the ONLY program at this time capable of determining a random MP3's original encoder (LAME, FhG, Blade, etc.). This is very useful, since different encoders work with different methods, i.e. produce different results, noticeable in the overall audio quality of the file.
Not only can EncSpot keep apart the different encoders in general, but also "sub"-encoders, which are different programs but work with the same codec (and they differ only slightly). Furthermore, EncSpot is able to show several other details of an MP3 file, such as the maximum bit reservoir, the number of short and long blocks and how many frames are available to each bitrate (VBR). Also, the number of joint, mid-side and intensity stereo frames.