So we know that the 10km ones are gold, the 5km ones are silver and the 2km ones have the orange stripe around the base. I’m not sure whether these differences are visible on the map before you pick them up however. Since I’ve been aware of the difference, I’ve only seen the 2km boxes on the map.
It would be useful to be able to distinguish because your inventory can quickly become filled up with 2km boxes, that don’t really justify the use of silver keys based on their aquisition rate. My preference would be to collect mostly the 5 and 10 km boxes for use with silver keys, and have a few 2km to burn thru with the gold key.
Hey Daesin, all of the Portmanteaus look the same on the overworld map. We’ve discussed this on the Discord server just now and folks from Australia sent screenshot of various Portmanteaus. All of them are same 🙁
The only way to know what you got is to actually to pick it up. And yeah, you should always burn through 2 KMs with a Golden Key.
We also put out a guide to help everyone with this: https://wizardsunitehub.info/wiki/portmanteaus-and-portkeys/

Yeah, I did a test yesterday too and came to the same conclusion. (I’m in NZ). Hopefully that’s something they’ll change in the future. Thanks for response.