There are keys which are simply used for tamper reduction. If you buy an RV in the United States, it will have lots of external compartments storage. These will likely all have the same key, as every other RV on the lot. Furthermore you can use your key to open all kinds of things! It's like a treasure hunt. Mysterious stainless steel panel on public restroom wall? Yep. Sprinkler controller? Yep.

And you can order them on Amazon for a wide variety of prices, depending on what function the are sold for. Sprinkler keys are cheapest. Security system keys are much more expensive. RV keys, in between. But all the same key.