1- genuine, made in China in 2003. Silver-tone hardware was available on some bags in the last 15 years
2- looks genuine, the first one I've seen from Italy and made in 1994. The font is correct for that particular plant
3- genuine, from China, 2002
4- a very early one from China, 1997. I'm not comfortable that the seller's Ebay photos can't be enlarged to show details. Sometimes that means that the photos have been "borrowed" from another site. I don't have any information on that style, and please note the seller's measurements are 14x12 inches. If it's actually only 14 inches wide it's smaller than a standard briefcase. I found one Completed listing that gives the same measurements so there's a good chance that they're accurate:
http://www.ebay.com/itm/Coach-0544-...D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557
EDITED TO ADD - Found the name, it's called a Compact Organizer Brief and it IS smaller than the standard size.
5- genuine Lexington Brief from 1996, made in the US
Noshoepolish might have more information. She's an expert on briefcases and may be able to suggest some possible problems to watch out for or to ask the seller about.
"Vintage" is usually considered 20 years old or more so technically none of these are really "vintage" although the ones from the US and Italy are closest.