Definitely the real thing.
Seen them in Bianchi dealerships round 94-96. Always quite fancied them actually.
Dedacciai Zero Uno, as the sticker says, is based around the 18MCDV6 steel alloy. Dedacciai started as a company when some key Columbus employees flew the coop and started up on their own.
It's a heat treated steel alloy in a similar vein to Reynolds 853. It was widely used on road bikes around the same period, but not something you see very often on MTBs.