Welcome to the forums
In regards to your K9, a photo (I'm sure folks would like to see it) or at least a description of it's appearance would help with a definitive answer.
I'm going to go out on a limb and say I believe that an "AE" prefix gun could certainly be carbon steel.
So if yours has a black finish and a flat sided frame like the K9 below (newer frames have a serpentine cut around the slide stop), I'd say there is a good chance it's carbon steel:
....of course you could always try some cold blue on a wear spot to verify that.
FWIW, if yours doesn't have a black finish, but has the flat sided receiver, some carbon steel K9 pistols came nickel plated.
Regards,
Greg