"I find it fascinating that a half century before lightweight metals became so popular for firearms, S&W was already making advancements in metallurgical usage."

Colt was working on lightweight aluminum alloy frames for automatics in the late 1940s, somewhat earlier than S&W was working on revolver frames. It was a much more complicated development project project than most would imagine. Colt worked with Alcoa for years before they came up with a suitable product, the Colt Commander in 9mm. The S&W Model 39 was not too far behind, but the aluminum frame did not work out too well.