It's rather close to ITC Symbol. Even Mixage is not very different. I imagine the letters have been tweaked a bit.

I downloaded the eps logo from here and looked closely at the letters. Here is what the S looks like:

This other logo is much better.

michel, that probably isn't a first-generation logo file, so it might not be best to try and judge the fidelity of the curves using that S. it looks like the postscript has been optimized and re-optimized several times.

> it looks like the postscript has been optimized and re-optimized several times.

What do you mean by "optimized". The eps logo whose characters have bad curves is more than 30 times larger than the one with clean curves? (1126931 bytes against 36487 bytes).