Finally got another chance to weight in my Ballast box. The reading is 679 lb (without anything else).
I usually put 3 Grade 70 chain (20', 15' and 5') and two landscape tools with it. Total should be over 700 lb for sure. It is very heavy and stable for me so far. I also found the H120 could pick it up without issue. I am ready to move forward on my project for the summer now.