As made & marked by S&W?,,or as modified & marked aftermarket for training purposes by L/E or Security, perhaps a theatrical prop, or for ownership in strict areas where non-firing handgun(s) don't require licenses,,,
Training firearms are usually colored in some manner to easily and quickly distinguish them.
With no serial number on this one & 'dummy' stamped in it's place,,I wonder just what the insides look like.
Not a real trick to modify a working revolver to the nonfiring condition this one is presented in.
With no ser#, this one should have not been a working revolver to begin with.
Just some thoughts.