I am new to this forum. This may have been discussed in the past, or it may belong into a different category. If so, my apologies.
   

I have looked at the wealthiest 100 bitcoin addresses (in terms of UTXO) and noticed a curious commonality between 8 of them. They are currently listed as #6 through #13.

What is it that they have in common:

1.    they all have a balance slightly above 66,000 BTC
2.   they have zero outgoing TX, never spent a Satoshi
3.    they all received their last input greater than 1 BTC in the time frame between 2014-11-12 and 2014-11-17. For each of them, this last large TX put their balances over 66,000 BTC
4.    they all have received fractional inputs since, but not many - maybe 15
5.    their very last input for each was on June 28th 2017, at 18:19:44, same block
6.    their first input TX was very close as well - for 6 of them it was on 2013-11-22, one of them on 2013-11-25, and the last one on 2014-02-24

Does anyone know or have an idea what's up with these? I was thinking, maybe a mixer? But that's a hell of a capital reserve, we are talking $1.2b. (I know the average buying price may have been 1/3rd but still). Also mixers need to send out some coin, unless ...

It's not the FBI's account (at least I didn't see any inputs from DPR 1FfmbHfnpaZjKFvyi1okTjJJusN455paPH), and not Mt Gox, I am pretty certain about that. Any takers?

Thanks in advance