I was watching an Uncle Doug video on You Tube where he works on a Recording King amp that has the blue Molded caps like '50's and '60's Fender amps. The Recording King is from the '40's as far as he can tell (though the title says it's a '30's amp). Anyway. It got me curious. What is the history of those caps? How are they made and what from? What makes them so special? Would those caps be original to that Recording King amp?