for a repeated cards, you should see an update in the activity log below the card which is a clickable link which you can open the source card. Otherwise, if there is no mention of copy, it is the original card.
Repeated card states the following on the activity log:
<user> copied this card from <source card> in list <source list>
Here's an example:
Let me know if you have any questions :)
If you had to thrive a new habit during a lockdown, what would it be? Trello
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