Yesterday, 80,000 BTC (worth roughly $8 billion) were moved on-chain. These coins date back to 2011, before the BIP39 standard existed. Back then, private keys were managed individually per address, with no hardware wallet support (even today). This suggests the keys were stored in a wallet.dat file, and the transaction was likely signed using a software wallet like Electrum. From a security standpoint, this is absolutely insane!