Nice find. I know a very little about the Napoleonic poeriod, mostly from the British side, and I'm a little surprised to see a stamped name plate/maker's mark on soemthing that early. I have no Italian, bar a few rude words, but the name 'Neapolitan Military Union' suggests a group or company to me, rather than a military unit.
I wonder if these might have been made for a military academy or something similar which wore/wears period uniforms. However, if they are the same as the pair you tagged on the web site, they're valuable and you should get some expert advice. Try speaking to a reputable auction house: send them the photos and ask what they think. Knowing where they came from might be important too. Good luck and let us know what you find out.