In 2000, Future Bee, Hudson (the software company, formerly HudsonSoft...hardcore, old school Nintendo and TurboGrafx 16 gamers will recognize the name) and Ahomaro Games launched the 2000 Power League Dream Stadium collectible card game. The set was issued largely as starter decks with 25 player cards and 25 action cards for playing the game (20 decks per box).
They then issued the "booster set" which they called Power League UL which was released in boxes of 20 packs containing 7 cards (6 base, possibly including an insert and 1 action card). The base set contains 195 cards and there were two insert sets for Power League UL, league leaders (25 cards, prefixed with 'T', representing both leagues) and Super Rare (36 cards, prefixed with 'S'). Both are shiny foil style cards that don't scan well (as you can see from the cards below). In addition to the contents of the packs, each booster box also contains one Super Rare Promo insert. The card below came as the insert for this box. The only apparent difference between the regular Super Rare and the Promo versions seems to be that tiny "PROMO" stamped right next to the card number on the back.
Working the math, one box should result in 21 insert cards and 100 base cards.