4506 Factory Magazine information needed

[dandor]

I just purchased a used 4506 factory magazine with the black plastic follower at a gun show this past weekend. It has a stamped "R" in the side of the body. I have several other 4506 mags and none of them have that stamp. Does anyone know what this stamp indicates? Is it a factory mark?

 

[lowwill]

Maybe for a remanufactured? All of mine have the S&W symbol. Also saying this magazine must have a yellow follower