This question already has an answer here:
If I have many files on my hard drive (possibly with different names/extension), how can I test which file is a valid bitcoin wallet.dat ?
Maybe there is some string that exists in every bitcoin wallet ?
I guess I am asking about the format of the data inside the wallet. If wallets are different depending on the bitcoin client, then I want to know about bitcoin core.
Edit: I forgot to mention but these files WERE on a Linux OS. So there should be some solutions.