Paul,
I believe you are right about the O2 Safe Shock but Jacks Magic only lists proprietary in their MSDS so it can only be guessed at. Howver, there are many similarities between their MSDS and the ones for sodium percarbonate. Also, they caution about using it in chlorinated pools but recommend it for biquanide and ionizer pools and for oxidizing black coper stains to a more readily removed form. All this is in line with it being sodium percarbonate.