Tom K...The left side of the frame has the same engraved line as the right side, but is covered by the left grip panel. I think Russ put the line in a slightly different place on the left side to avoid cutting into the S&W logo, or he just put it there and the stocks cover it. The stocks are original and numbered to the revolver.
Since the revolver is covered with "standard" Class A-engraving, and not a custom piece, I suppose no one paid any attention to the fact the line was in a different location. I hadn't noticed it until you pointed it out.
Bill