[Chas]

Modern metalized capacitors do not expose an electrode to enclose the body like early paper capacitors. They are of a stacked construction, therefore there is no outside foil by definition. Consider if there were an "Outside Foil" the manufacturer would have indicated.

https://en.wikipedia.org/wiki/Capacitor_types

https://en.wikipedia.org/wiki/Film_capacitor

Though it matters little to restoration of domestic radio, choosing the correct replacement capacitor for the "all purpose" paper/foil capacitor is routinely the inexpensive metalized plastic film design. However, that type is not as universal as the paper once was...

Restorers are aware to use the "Safety" capacitors on AC line bypass, it that, it fails "open".

I am, too, squeamish about installing metalized without an outside foil. I "feel comfortable" by simply orientating the legend in the same direction as the paper capacitor it is replacing, silly, but I have not had a coupling/hum/noise issue, yet.

Common metalized cannot withstand serving in a pulse environment. The rise time of pulses that can appear in the output circuit of a radio can cause the metalizing to break-up, yet the film not puncture or short. This causes a loss of capacity and in some instances noises, (random ticking) actually a short train of pulses generated by the metalizing connecting/disconnecting.

For such purpose as pulse service, there are metallized of special internal construction or the use of a foil. Sounds all good but the foil/(plastic) can fail shorted and not clear the short like a metallized can.

Chas