Easy way to Improve the tone of your amplifier with these vintage capacitors! 

It is enough to pay attention to one detail and understand how superior they are compared to anything from today's production.

Glass End Seals, shown in the photos.

Made almost 6 decades ago, they still have all the characteristics within tolerance. Even then, these capacitors were many, many times more expensive than "ordinary" capacitors. The difference is, that at that time it was covered by technological solutions and expenses of processes, and today it's just marketing ploy.