According to White Collar Wiki "The show's costume designer Stephanie Maslansky openly discusses the makings of Neal Caffrey's wardrobe on White Collar's official website. She says his look is 'mid-century gone modern' with suits by designers John Varvatos and Paul Smith (but let's not forget about his vintage Sy Devore suit from the very first episode). His tie bars are vintage, and his ties are also almost always vintage and bought at Manhattan's Star Struck and Cheap Jack's." I know Brooks Brothers is mentioned a ton in the show(referring to the FBI agents' suits), Thomas Pink shirts shows up in an episode or two, and I think there is a Valentino reference thrown in somewhere. I believe there is a good amount of Varvatos in Mozzie's wardrobe as well.