Brass knuckles can be a useful tool in a punch-up, to unequalize the odds, but strangely many jurisdictions frown on their owners.
To be found in posession of same may result in awkward questions.
It would therefore be advantageous to have a set of brass knuckles that do not, in fact, actually
look like brass knuckles.
Now, BorgCo engeneers have perfected such a device. It's a set of "brass knuckles" manufactured from shape-memory metal alloy with a transitional temperature of 30C. They are supplied as an inoccuous-looking design such as a novelty giant paperclip keyring, but on being warmed against bare skin will revert to a more utilitarian shape.
After use, just pop the item in the reply-paid padded envelope and mail it back to BorgCo. You'll receive a replacement item by return, while we charge your credit card a small amount and autoclave your original unit to destroy any evidence before re-bending* it and sending it out to another customer.
*Attempting to re-bend the metal yourself will invalidate the warranty and the results are very unsatisfactory in the vast majority of cases.