Thanks to many who contributed screenshots, I was able to record 1270 Super Sigil chests, all of them opened during the PvP/KoTH event weekend.
Here are the key stats. On average, 10 Super Sigil chests yield:
- 400 Spring Season Sigils
- 2500 Egg Tokens
- 240 hours of speedups
Compare with Gold chest stats that I posted earlier here. It surely looks like Super Sigil chest indeed drop 2x more sigils on average.