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The difference is: they'll be temporarily marked with '?' since they may be invalid until the node sync to the height where the transactions were.
So, there's a chance that it's really Bitcoin unless the wallet.dat is from "Litecoin Core" or "SegWit2X Core" clients because "Bitcoin Core" will display them as Bitcoin even though they're not.
@nadeto3719 you can get the transaction IDs of those transactions from the 'Transactions' tab by using "right-click->Copy transaction ID" and paste to a multi-blockeplorer to know which coin they belong to.
For that, use https://blockchair.com/ for Bitcoin and Dash, i don't know any blockexplorer for the dead coin SegWit2X.
If it's Bitcoin, the best and safest way to go is to let Bitcoin core sync.