In the SanKen data sheet for an Off-Line PWM Controller (found here) they use, in several places, a schematic symbol for an electrolytic capacitor that I haven't seen before (see C6 in the image below).
The image was taken from Chapter 12. Reference Design of Power Supply. And from the Bill of Materials they list "C6 Electrolytic 22 μF, 50V".
What is the meaning / significance of the the three slanted lines on the capacitor symbol?