I agree the case looks fantastic. With regard to the trigger guard and backstrap, I believe all Colt 2nd Generation 1851 Navy's had brass trigger guards and brass backstraps. The vast majority of them were of the squareback style and were silver plated. There were small numbers of plain brass squareback, plain brass round trigger guards and silver plated brass round trigger guards.
There might be a copper plating underneath the silver, I know that nickel plating often uses a copper layer underneath so I guess it's possible silver plating might also use it. Also be aware that silver plating can tarnish to the point that it actually looks like blued steel.
