S&W's revolvers with externally accessible hammers have the ILS (or, the 'lock').
Some of their Centennial style revolvers, having internal hammers, are often offered in models both with & without the ILS.
As it was once explained to me by someone from the company (in a class), if you can reach and thumb-cock the exposed hammer of a revolver, it's going to have an ILS (lock) in the frame.
Naturally, S&W corporate may one day decide to change their mind about this, and deviate from what's been described as being advice received from their corporate legal folks, but this isn't one of those hold your breath, things.