7Eleven - Movie21 Poké Ball Promotion (Master Ball set) .

When players purchase 2 relevant ice cream products at 7-Elevens in Japan,
players get a clear file relevant to Movie21, and a serial code that gives away Poké Ball x100.
Additionally, it was announced that there's a chance for the gift to yield Master Ball x1 and Poké Ball x99 set.

How the mechanics for that work, is that a set of 5 wonder cards were bundled together,
with 4 being the Poké Ball x100, and 1 being the Master Ball x1.

Player's game-save stores which set has been obtained, and the chance of 1/5 increases to 1/4 and so on, per missed Master Ball x1 redemption.
This means, players will definitely get the Master Ball x1 by their 5th redemption, on the same save file.
After the full set of 5 has been redeemed, the whole receiving set information that was stored resets,
and the chance of receiving the Master Ball x1 restarts from 1/5.

WC 297: モンスターボール100コ　プレゼント

Master Ball         x 1

0x2C Thank you for playing Pokémon! Please pick up your gift from the deliveryman in any Pokémon Center.

Poke Ball   x99

Serial Code  |  Jul 10 to Oct 01, 2018  |  JP 3DS: SMUSUM

Format Ver.1.0.6-3, Post Updated Date:20180711_0436