DUF, seeings how both the reg and milreg (and I guess the TT version as well) were all SR101 I would guess the Bulldog would be as well.

Personally I have never been worried about rust on any blade that I have carried, even in leather sheaths. Just check them at least once every day or so and you shouldn't have any rusting problems that would impact on the knife in any way that would be detrimental.