SS = 19 19 or 99 (advanced) or 11 (highly advanced, or thus 77)

But also (also advanced, the flip) 99 = 66

Note, you got there, by other means, below. :)

"99 = 9+9 =18

99 = 9x9 = 81

81+18 = 99

Reverse 66"

Note in both 18 you have our keys and in reverse #occulted in 81. ;)