confirmed...


"That brings up another question that comes up all the time. What's the real difference between an SM57 and an SM58? There are actually a fair number of myths and misconceptions about what the difference really is.
The basic difference is the grille. The other parts -- the diaphragm and voice coil combination, the magnet, the transformer that's in the handle, the handle itself, the closing ring that surrounds the cartridge – are identical.   

In the SM58, the ball grille with the foam lining provides an extra degree of pop protection and wind protection. The SM57 has a much more compact grille arrangement that doesn't provide nearly as much protection against blast or wind.   But the basic frequency response and polar patterns are almost identical – there is only a slight difference in high frequencies where the shape of the grille starts to affect the response. But that probably doesn't kick in until 13, 14 or 15 kHz – something like that. "



http://www.shurenotes.com/issue30/article.htm