Mystery Finest
Cards from this 90-card set feature color action photos of top players on double-sided cards. Each player is matched with three different players on the opposite side or another photo of himself in each series. Each side is covered with the Finest opaque protector that must be fully removed on both sides.
In the first series, 50 Mystery Finest cards were randomly inserted; while in Series Two, another 40 cards were produced. Unfortunately, Topps re-numbered the Series Two cards as its own distinct set, with a similar design and the same card numbering scheme. to distinguish between the two series of Mystery Finest cards, all 50 Series One cards have a "wave" design, while the Series Two cards have an "arch."
Each card is also available as a Refractor.
Series Two
M1 Nomar Garciaparra / Frank Thomas
All the above was taken from Baseballcardpedia.com
The one with Nomar is the back of one mystery finest. The front should have Frank Thomas on it when peeled off.
The double-black would work the same way...you have to peel it to find out what it is.