They call those "tops", I guess because you only see the numbers on top, so the duplicate numbers aren't noticed. If you can find an old copy of Scarne on Dice you'll have a very good idea of how they were used in play.

Some combinations will be passers that will always make points and some will be bust-out pairs. I can send you more info later.

From what I've seen, the ones with club logos stamped on them are pretty hard to find. The unmarked ones are much more common, but still a nice find. If you decide to sell any look me up.