Wow. I suspect you are vastly underestimating your find. Or maybe you should get Sotheby's to take a peek. That's a near one of a kind with the badging that is on it.
I have heard of the Kimberly pit. A lot of my working life was spent around mines and their equipment. Kimberly was/is thought of as the largest ever hand dug pit.
haha, I think the market for these scales is not so big any more, I've priced it quite high, so we will see if it goes soon!
You are spot on there - it is the largest hand dug "hole".