I got my M series Sub engraved......i negotiated it as part of the purchase.....and so it did not cost me a penny!!!!!....i never asked what they normally charge.
It was the AD at Millenia Mall.....unfortunatly it closed in Dec and as of a few days ago, has not re-opened.....Park Promenade.(upstairs)
On a related point.....some people believe(i am not one of them) that detail on the case back helps the watch not to slide around on the wrist.I think if it is sized correctly then it is not an issue.