Ok, so it's not a rainbow in the traditional sense of piles of meaningless, slightly different variations, but who would have thought such a set so far out of the collector's main stream would have three different variations?
In 1991, Score issued a set of 10 supposedly up-and-coming prospects that were expected to make some sort of impact over the next few years, and they were given away at the 1991 All-Star Fanfest over the MLB All-Star weekend in Toronto, in a little sealed plastic wrapper like Post used in the 90s for cards issued in cereal boxes. They also came with a random 1991 Score World Series trivia card like were issued in every pack of Score. To save a little effort, they also gave out pretty much the exact same set at the 1991 12th Annual National Sports Collectors Convention in Anaheim, California. The only difference? That little line of text on the lower red stripe on the reverse of the cards. Incidentally, Score also produced a set of hockey cards, featuring some of the greats of the day, using almost the exact same design (the colors were slightly different).
I'm guessing the last one was perhaps a proof or example printed up without the lower banner to show how the cards would look. I bet they were never intended to see circulation amongst the general public. While I've seen several of the Fanfest and National sets once I started to notice them, I've seen this particular variation blank variation listed once on CheckOutMyCards.com. Of course, that may simply be because no one ever posts scans of the backs of cards on eBay or Sportsbuy.
Here's the full checklist of the sets, in case anyone might be "super collecting" Ed Sprague:
Score Title Card (blank backed)
1. Ray Lankford
2. Steve Decker
3. Gary Scott
4. Hensley Meulens
5. Tim Naehring
6. Mark Whiten
7. Ed Sprague
8. Charles Nagy
9. Terry Shumpert
10. Chuck Knoblauch
I almost have to think they were shooting for the 2nd or 3rd string of actual prospects....I mean, this is 1991, and no Todd Van Poppel? No Jeff Bagwell? I-Rod? Mo?
Beckett doesn't acknowledge the existence of the National set, but SCD lists both sets together, mentioning the separate events. Neither mention the existence of the blank variation. I have no idea what the print run was, but I imagine loads of these sets didn't survive any farther than the trash cans by the exit doors at the events (especially after kids opened them and saw who was in it!). In 2006, SCD gave the set a whopping $2 book value. Beckett was a little kinder, but not by much. The Fanfest set is pretty easy to find on eBay, the National set slightly less so.