Mercadian Masques is a large set with 110 commons, 110 uncommons, 110 rares, and four variations of each standard basic land. This is the normal size for a large set of this era. Foil cards are included in booster packs with advertised odds of 1 : 100 cards. The set was printed in the USA and Belgium.
Mercadian Masques was sold in 15 card booster packs. Booster boxes have 36 packs.
The US and Belgian printings use the same collation method. They use striped collation with 10 × 11 sheets. Packs are back-facing and contain 3 uncommons, 1 rare, and 11 commons (in that order). Foil cards are inserted only between stripes (in other words, after a card on the left side of the sheet before moving all the way back to the right), displacing a card of the same rarity. It is possible to get multiple foil cards in the same pack. Foil basic lands can appear instead of a foil common. Non-foil basic lands do not appear in booster packs.
|3 Uncommons||1 Rare||11 Commons|
Tournament packs have 3 rares, 10 uncommons, 32 commons, and 30 basic lands in addition to a rulebook. Observed packs are front-facing with lands followed by rares, uncommons, and commons. There is a rules insert between the rares and the uncommons and a survey insert between the uncommons and commons. Packs have both an inner and outer seal. (Note that I haven't observed US tournament packs.)
Foil cards in tournament packs behave in the same way as foils in booster packs, except foil basic lands appear in the lands instead of in the commons.
|30 Lands||3 Rares||Rules Insert||10 Uncommons||Survey Insert||32 Commons|
There is a single sheet that prints each common once. The top row is chosen to prevent blue cards from appearing next to each other on the sheet.
There is a single sheet that prints each uncommon once. The choice of top row is mostly arbitrary.
 The "Compilation of Manufacture Information for MTG Products" thread on the Magic Librarities Forum confirms the existence of US tournament packs.