Probably for timing/pulse stretching.

The schematic does NOT show a polarity on that capacitor. Is it an electrolytic type?

Ah.... it's a non-polarized (a.k.a. Bi-polar) electrolytic. That means it's being used with AC power.

Somebody should add the designation "B.P." or "Non-polar" to the schematic next to that capacitor.

It looks to be in good physical shape. A capacitor "value" reading meter could be used to test it. It's probably ok.