Can someone identify the model number of this S&W revolver?

[Rockrivr1]

When my uncled passed away some time ago I was given his service revolver, which is a M15, and this 22lr revolver. When you open the cylinder there is a stamp that reads 6-A. I don't think it's a Model 6. It's a 22lr with a 6 shot cylinder. I've attached a picture to help identify it.

Thanks for the help.

 

[Shear_stress]

If that's a 22LR and has no model number, than you've got a K22 Masterpiece made before 1957. "Masterpiece" is no misnomer. These are very, very fine revolvers.

 

[thatguy]

Pre-Model 17.