Don, I am usually not too concerned over silvered mica capacitors (though I have come across several with ‘silvered mica disease’ which causes lightening-like loud crashes in the speaker!). However, ‘Micamold’ was an American company that produced a variety of capacitor types, including paper and silvered mica dielectric capacitors. Many of their ‘domino’ style capacitors looked like silvered mica capacitors, but were actually paper dielectric (and pretty lousy ones at that), and should always be replaced. See article here that mentions these and how to replace them (pages 8 and 9).
