[cesarb]

If this was a really old Bitcoin wallet, it could be from before the "12 words" thing. IIRC, older wallets randomly generated each key, instead of deriving them from a seed passphrase (which also meant you had to be really careful with your backups, since an old backup of the wallet wouldn't have its newer keys).

[rufusroflpunch]

I am sure you’re right. But you could just send the funds to a new address in the new wallet. He could have done that at any point in the last 5+ years.