[Magic Item] Tymora's Copper Coin of Luck

I don't know if there is an item like this as I have not read every splat book out there but I thought about creating this item for one of my players. I was dropping a shiny coin at shrines and in encounters to add a bit of curiosity for the player.

Tymora's copper piece of luck is a magic item that is often left around by the goddess for travelers to find or lucky followers to gain. The copper coin version is a magical coin of local denomination and of faint enchantment that has the following effect:

Whenever the player rolls for advantage, they can "save" the lower, discarded result into the coin. Whenever they have a disadvantaged roll, they can swap the saved result for the lowest of the two rolls. After the coin is used this way it becomes just a copper piece. Have the player make a note of what roll was saved into the coin.

Other coins of luck may be possible.

How this works: Player rolls advantage with a 13 and an 18. Chooses to save the 13 into the coin (18 is active roll number). Then rolls disadvantage with a 6 and 15. Coin replaces the 6 with the 13. 13 is lowest so becomes active roll number and 15 is discarded.

What is the general consensus from everyone?