I'm assuming it can cause something to happen immediately or grant some sort of ability and you can't know exactly what.
I don't understand aversion to admitting what box you have here.
Firstly, there are more town than mafia, I'm assuming, so being open about boxes and how we can use them effectively might be our best interest.
Second, we all should be brainstorming what these boxes could do. Let's say CDM has a really cool sounding box, something that sounds like it will benefit him greatly, well this may just be some Needful Things scenario, as there's always a price to pay and something you may not have expected.
Not claiming what your box is, isn't necessarily anti-town, I'd argue the initial aversion to claiming it to be fairly town. But these boxes don't carry scum/town weighting, so it's all equal footing. Knowing who has what box and effects that may happen overnight can give us a much better idea of what is actually happening. Yes, mafia will have some knowledge, but I believe full transparency on the box issue is a much larger benefit to town than mafia.