As you say if it's had a polish you should see it. If the polish was done so well you can't then so what.
Now I've done some cold blue on worn shotguns not worth a caustic blue that came out rather well. Hard to see at a glance but there will always be some variation in the depth of blue I don't care how good you are. Possibly somebody in it for a quick resale wouldn't pick up on it.
As far as lettering goes, I've seen some poor roll stamping on firearms that you'd think deserve better.
