The general calculation is inverter wattage divided by low battery voltage divided by 85% inverter efficiency.
So 1200W inverter on a 12V battery would be 1200W / 12V / 85% = 118A. The 85% factor is real conservative. Victron inverters are usually over 90%. But using the lower factor helps you choose bigger wire and fuses resulting in a less stressed system build.
Victron tends to measure their inverters in VA (volt amps) not W (watts). In their case VA x 80% = W. So a 1200VA inverter would be 960W. So that's 94A.
The SOK should be fine at 118A and definitely good at 94A.