ltc44, according to an article I read recently, Colt beat S&W to the punch, with a bolt-on hammer shroud for its D-frame revolvers. S&W followed suit with the original Bodyguard model J-frame, which looked more graceful as the shroud was integral to the frame.
The Centennial was based on stretching the I-frame Safety Hammerless to take the .38 Special, as opposed to the I-frame's .38 S&W. Eventually, the Centennial and its descendants evolved to lose the grip safety from the original design, too.
One reason I like the 442 is that it has virtually nothing that can snag.