Wardrobe and description from Star Wares:

“This is the screen used white Giorgio Armani silk handkerchief worn by Robert De Niro in his pocket as Al Capone in the film The Untouchables. It has been notated in ballpoint ink on one area...”

De Niro, a method actor, insisted on wearing suits provided by Capone’s original tailors. He even wore the same style of silk underwear as Capone regardless of the fact it would never be filmed.