i can ask my father, he's a great attorney and knows from this stuff.
I feel maybe they think, the name on the product (the mint company) since you are retrofitting something, without contracted agreement, is infringement on thier design or brand reputation. I can't like make an mp3 player, put it in an ipod case, then go and sell it as something else. Apple would own me.
Yet i think they won't bother with you guys, why would they waste money, when there is little to money to made off of suing you (in the idea of what it would take to go after you, its useless)