The 2-Player Starter Set includes 61 cards unlike the Theme Decks released alongside Base Set, which include 60. As the 2-Player Starter Set is designed to introduce players to the TCG, the cards are split into two 30-card decks: The First Deck, which focuses on Pokémon, and The Second Deck, which focuses on Pokémon. As the only Stage 2 Pokémon in the set, the additional Machamp card is included to bolster the deck. The 2-Player Starter Set also includes a starter rules sheet, rulebook (v.1), damage counters, and card list. The set does not include a coin, though none of the Pokémon found in the set require one for any of their attacks.
The Machamp card can be used when you put the 2 half decks together. Remove 1 card you won't miss and make a full 60 card deck.
The Machamp card is exclusive to the 2-Player Starter Set, and can not be found in Base Set booster packs. Two variants exist of the 2-Player Starter Set: the first printed variant included Shadowless cards, including the Shadowless1st Edition Base Set Machamp. The second printed variant included the "regular" 1st Edition Machamp. This card was only ever printed commercially as a 1st Edition variant, with the only Unlimited variant included in the Trainer Deck A.