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You can find out pretty quick if it's carbon steel or not; leave a small drop of water on it. Like underneath the tang or something, clean it off if it starts tarnishing with some metal polish.

No experience with SS razors or Fillys, but Bigspendur is correct about the sub cero thing. Carbon steel really doesn't ever get cryo treatment, so I'd bet it is stainless.

Edit: ya beat me to it,...