Closest I could get was that the K-4, when it was in production, was at 40 gallons capacity and weighed 750 lbs. plus 65 lbs. for jackets.
And one up in size, the K-6, was at 55 gallon capacity and weighed 950 lbs. plus 75 lbs. for jackets.
All 3 boilers have 6 steel plate sides, so vessel weight doesn't go in half when volume goes in half, and so forth.
The 24 gallon Kaa-2 is 1/2" less in width, 7" less in length and 11-1/2" less in height than the 40 gallon K-4 that weighs 750 lbs.
So...the Kaa-2 at 24 gallons volume...I would guess
...around 500 lbs. give or take.
I still would welcome someone who knows the specs. to weigh in. (no pun intended)