To get things started, let’s take a look at the enigmatic, and Topps Heritage-esque, 1990 Bowman Baseball Set:
It took me almost 17 years to notice the approximately 100 different variations found in this set. Many longtime collector’s who own an annual price guide already know about the semi-rare, David Segui #251 with his bio information missing on back. This interesting error is the only one like it in the set and currently lists at $3.50, though I’ve seen them sell for much higher and and a little lower at times. But what many collectors don’t yet know of, is that Bowman issued 2 different versions of several of the subjects in this set. Like today’s Topps Heritage line, some of the players can be seen posed against night backgrounds and daytime backgrounds due to some expert airbrushing. Some players sport both gray and white jerseys on their cards and a handful of players had troublesome light posts and clouds airbrushed away in their backgrounds.
Robin Ventura #311 has had his background and jersey re-touched by Topps’ editors.
Pete O’Brien has seen his jersey go from gray to white in subsquent printings.
Now, these are just a couple examples of this type of variation found in the set. Many stars like Don Mattingly, Dave Winfield, Nolan Ryan, Rickey Henderson and Matt Williams for example, are all affected by Topps’ mysterious editing choices for this set. Almost all of the Detroit Tigers and Minnesota Twins players have had their jerseys altered from gray to white, and in the case of some Twins, their pinstripes have even been removed from their jerseys!
Some other oddities to look for:
#29 Mark Grace: Bowman removed a black bar originally printed on his hand.
#34 Earl Cunningham: Originally had an asterisk after the word “in” on back, but was changed pretty late in the run.
#399 Dave Parker: Can be found with or without his copyright line on back.
#NNO Doc Gooden Art Insert: Can be found with the word “$100,000” missing on back.
Since the discovery of these variations is relatively new, a true market value has yet to be established but a few mentioned above have already seen bid amounts that exceed the entire set’s book value. For the time being, aproximately 100 different variations have turned up with several more probably out there waiting to be discovered. Even if they weren’t produced in scarce quantities per se, a master set of this variation-laden issue would be a worthy accomplishment and a great addition to any collection.
Junk Wax Gems 
Awesome site. this is my 1st time here and am very impressed at the amount of information on error cards I did’nt even knoew about. Anyways, I just found an error card yesterday and I have researched all possible sources on this card and I got nothing. Maybe you can a little light on the subject. it is a 1990 Best Cards Minor League set # 23 Shelby Hart of the Everett Giants. On the front of the card his name is spelled Shelby Hard and on the back his last name is spelled Hart. Also, I grew up in New Jersey, about 20 minutes outside philly. The town next to mine has had a handfull of athletes turn pro, including one that I grew up with and have always, even to this day, kept in contact with is Malik Allen of the Denver Nuggets, not a big name but he has been in the league for almost 10 years now and was signed by the Heat to help replace an ill Alonzo Mourning, and actually did pretty well considering the shoes he had to try and fill, and like most players his size he had a few injuries and eventually was traded to the Bobcats to make room for the arrival of Shaq. The town he Sean Casey(Reds), Carl Lewis(Track star), Franco Harris(Steelers & Hall Of Famer), Irving Fryar(Patriots, Eagles,Dolphins),Bryan Ward(Pitcher- Marlins,Cards) were all born in Willingboro, NJ. Some of their cards say Willingsboro, with an (S) in it. So I think they would be errors as well.