there are AC electrolytic capacitors, rs still sell them? they are just not used much, it looks like its a paper capacitor?
Bush TV43 Hum Cancellation Cap
https://www.vintage-radio.net/forum/...ad.php?t=71267
http://en.wikipedia.org/wiki/Electrolytic_capacitor
Bipolar electrolytics (also called Non-Polarised or NP capacitors) contain two anodized films, behaving like two capacitors connected in series opposition.[12] These are used when one electrode can be either positive or negative relative to the other at different instants, on alternating current circuits. Bad frequency and temperature characteristics make them unsuited for high-frequency applications. Typical ESL values are a few nanohenries.[13]