bricklayer
I have carried both Gold and Silver domestic and International, multiple times.
Never had a problem. Have been asked to have a look in the bag maybe 10% of the time. Only once did they remove the Silver and re-screen both bag and Silver. That was at a country airport.
Lets be honest about this, do you really think there are people interested in your or my bag check and re-screen ?, do you look at what people have removed from their bag and put in the tray?, I don't
I think you are way too paranoid and bringing attention to yourself by asking for a service which should be available but the bozo's who work there are not familiar with.
Departing Sydney about a year ago to Asia, had about 100 oz in various coin sizes including a 1 kg coin. I went though and waited for bag, watching agent at screen, saw his interest visibly pick up, scratch his head and turn to look for owner of bag, saw me smiling at him, he pointed to the screen and said is this yours. I said yes, silver coins. He said they are big, I said yes you want to see ?, he said no and waved me off.
Even if someone were to notice you had silver or gold in your bag, whats the chance they are even on the same flight as you ?
Airports are full of people all stressed out by the experience and only really interested in their own objective which is going somewhere, not looking for an opportunity to rob anyone or take notes on anyone.