Agreed.........but I always get twitchy when people go to that length to obstruct numbers on Firearms, so unecessary and spoils a good rifle, unless the seller has something to hide.
I would probably bet I could recover that number in my old job at the Home Office, recovered a lot worse than that.
On serious crimes we applied an etching re-agent, generally a strong acid whose name escapes me at the moment, and the metal around the stamped out markings which were etched over or eaten away by a hammer by the acid leaves the compressed metal intact and visa vi the complete serial number. Scientific magic but it works everytime. The cut of a serial number into any weapon shocks it to its very core and WILL ALWAYS leave a trace, some better than others.