On a mint, original finish gun, I would expect to see raised areas around all lettering (very slight) and very sharp, raised feeling to the S&W trademark stamp.
The hammer and trigger should have strong color-case hardening. The pads on the extractor should be in the white, not blued.
The stop notches on the cylinder should be knife sharp with no softening of the edges.
Machining marks should be visible on front of cylinder.
Most of these observations are somewhat subtle, but the more guns you look at, the more detail you will notice.