Yes, the all stainless PILS razors have been known to rust - I had one that did - but I have never seen an explanation from the company as to why. You can see an example here: http://badgerandblade.com/vb/showth...NE-and-Morris-and-Forndhan-Horn-Handled-Brush.
I believe the non-stainless models are nickel plated brass. http://www.royalshave.com/p/401-086-00/pils-safety-razor-101nn.html
P.S. I am not sure if you can still find them, but iKon made a PILS clone called the Modern, which was made from a marine grade of stainless steel that I guess is rust proof (or was advertised as such). http://www.italianbarber.com/ikon-shave-craft-modern-razor-with-deluxe-leather-case
P.S. I am not sure if you can still find them, but iKon made a PILS clone called the Modern, which was made from a marine grade of stainless steel that I guess is rust proof (or was advertised as such). http://www.italianbarber.com/ikon-shave-craft-modern-razor-with-deluxe-leather-case
The explanation from the company.
"Regarding the rust, it was not a general problem, only a few customers unfortunately had some problems with the rust that occurred on their blades. To make our razors even more resistant against rust from the blades, we now developed a special method to protect the inner surface of the razors. While we cannot completely exclude the encrustation of the rusting blade on the material, it will definitely be easier to remove it. In general, we suggest to carefully clean the razor after shaving and to let it dry completely, as well as apply a special oil from time to time to further protect the inner surfaces. "
Whether that is true or not, it remains to be seen. But there ARE some people who did not have any rust issues.