K frame dating
To do so, we have to go back a few years to the beginning of the Magnum era.
The L-frames, engineered to handle the stresses of the .357 Mag., deserve to be understood by today's handgunners, so I'll tell their story here.Long-barreled versions of the revolver drove 158-grain bullets to speeds of 1,500 fps or more.Essentially the Magnum was a stretched .38 Spl., but the performance improvement in both gun and cartridge quickly developed enormous popularity. People began to regard the .357 as a gun/cartridge combo capable of expanded roles such as long-range shooting, dangerous-game hunting and anti-personnel use.It was a brute-strong gun, fitted and finished to an unprecedented level of excellence.
The big N-frame wheelgun fired a new, high-speed, heavy-bullet cartridge called the .357 Mag.