OOOoooo, I like!
I am a Colt Python owner but will be first to admit there's nothing like a S&W action. I also own a Mod 17 and a Mod 34 Smith in .22 and shoot the heck out of these.
The picture you sent is definitely the Model of 1955 .44 Maggie, however the Model 21-4 is the Model of 1950, which will have a skinny barrel, fixed sights, and a round butt. It will probably also have the new internal safety.
Nice picture BTW.