I understand your request is about old wallet.dat files from the era of BitcoinGUI when there were no HD wallets common. Correct?

What exactly is the recovery scenario?
Do you need to scan storage media for fragments of (possibly deleted) wallet.dat files?
Or do you need to repair damaged wallet.dat files?
If you have wallet.dat files: where are those from?

I started my Bitcoin journey somewhere in 2011 and have a wallet.dat file that was created in 2011, but I might not have a backup of the file from 2011 or 2012. This wallet was in use until around 2013 or 2014, then dormant for some years and upgraded to current Bitcoin Core versions somewhere in 2020/2021 and emptied in 2021. That's probably not what you're looking for and I won't give it away anyway.

I might have other, likely unused, wallet.dat files I created, maybe in 2012. But I'm not sure if I haven't touched them with a more recent version of BitcoinGUI or Bitcoin Core when checking if they're really empty or not.