As we are talking "top drawer" and "Rolls Royce" here, the thought occurs to me that you need to have a good look at those buttons. IF they are original, IF, I say again, they could well be silver, have a good look for hallmarks, just in case. Failing that, they could still be older than most buttons on Highland wear, even if they are silver plated(?), or, some shiny silver colour, or quite likely, someone has replaced the originals with modern ones. Shame one is missing just the same.