The Twenty One is a beautiful radio and one of my very few that gets daily use. I had my first one for years and then someone offered me a new one still in its box with the original price tag. Couldn't resist, so I upgraded to that and sold my first one, which is described in this article.
http://antiqueradio.org/KLHModelTwentyOne21FMRadio.htm
You can see an original filter cap in one of those photos.
Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html