Big Key Tag

With such a label, the key will be very difficult to lose!
The round, flat design allows you to conveniently place anywhere. 

And using bright colors for printing, you can always distinguish the keys.

The central recess can be used in completely different ways. For example, you can write with a marker or print on a paper printer, and paste the necessary information. Or you can add text to Prusa Slicer when slicing the model.

But if you want more personality, I recommend using 3d printed tokens. You can create your own, individual design or use tokens from my collection.

If you will create your own token: diameter 50mm and height 2 mm. It is better to leave the margin ~ 2 mm from the edge empty, or make a side (see sketch).

To fix the token, you need to print the insert_ring part, made of TPU or other soft plastic. Then insert the token into the ring and snap it into the Big Key Tag.

Update from 11.10.2023
I added another mid_key_tag model. It is slightly smaller than the main model, and a TPU ring is not required to install the token. Replacing a token in this model is a bit harder.  It fits better in your pocket, but still remains the same noticeable among other things.