Post 12 doesnt look like the front sight was removed to me. Those arent typical marks that I have seen with front sights that were banged off, IMO.

As for the sandblasted barrel theory, It may be plausible because surface prep does effect how a certain finish appears,however I dont think there is any part of the front sight that would drag across this area when it was pressed on. The key would have been put on before the sight.