Keep a copy of the DAT file and try with Dogecoin. If it does not work then try with another possible wallet you have used before. And I don't think I understood your first query.
So I guess there is no way to open the file with a text editor and understand from its content which crypto wallet this file refers to?
As for the first query, here is what I did to check the balance of these files. I moved each wallet.dat file in the Bitcoin Core directory. I then opened the client with no internet connection and I copy/paster all the addresses in the Sending and Receiving section of the client. I then copy/pasted each address into blockchain.info to see the current balance. All addresses had a 0 BTC balance, except one address that I found in the Sending section of the Bitcoin client.