Preview/Prototype/Promo cards are all essentially the same thing. During the 90s and early 2000s, it was fairly common for card manufacturers to make these types of cards to promote new sets coming out later in the year. The cards were typically distributed directly to dealers or handed out at shows, and sometimes in earlier products from the same company, to get people interested. Now most card companies just use their web presence (social media, blogs, websites, etc) to show off upcoming products.
Collecting John Stockton, Karl Malone, Ivan Rodriguez, Gary Carter & UF player rookie year cards. Plus Jedd Gyorko rookie and prospect cards.
Jedd Gyorko 2010-2013: Have 329/419 including 1/1s
Wantlist: http://sites.google.com/site/sportscardsite/set-needs/
Jedd Gyorko 2010-2013: Have 329/419 including 1/1s
Wantlist: http://sites.google.com/site/sportscardsite/set-needs/