capacitor marking on a MICA Cap question?

[innkeeper]

i ahve a bag full of these mica caps

there marked as follows

220 ±5%
         EM

ok so 220 means 220pf and +/-5 is the tolerance
but what does the EM mean?

there are no other markings on this cap, no voltage markings, brand names etc.
I am guessing EM may be a voltage rating code???
anyone know more?

[Tac Eht Xilef]

Manufacturer. "EM" = Elmenco (Electromotive Corporation). Owned by Arco, then later IEC Servicemaster.

[innkeeper]

awesome thanks!