There are a lot of assumptions.
I did not do anything to account for deformed lid or even it tumbling which it probably did also.
Other have pointed out other assumptions that must be made.
However, contrary to what one poster seems to believe I suspect the government is doing detailed simulation and reconstruction analyses on the bomb event to determine stuff like how much explosive was used, how much inert mass was involved besides the cooker, etc. and then trying to match up those results with the video and photo evidence... or vice versa.
My cut was a 15 minute SWAG so take it for what that's worth.
Our family's journey from the Rocket City to the Redoubt: www.suburbiatosimplicity.com