4 printings of Undo
They range from $0.14 to $0.43 — a 3× difference for a card with the same name. The set code and collector number printed along the bottom edge are what tell them apart.
| Portal Second Age | P02 59 | $0.43 |
| Starter 1999 | S99 58 | $0.30 |
| Visions | VIS 47 | $0.14 |
Not sure which one you are holding? OtterDex reads the set code and collector number off the card and tells you.