The Number of Artifacts
Although there are 100 uniquely different artifacts, in any particular RSW game there might be fewer than, or more than, this number of artifacts actually distributed throughout the galaxy. This is loosely based on the number of players in the game.
A 15-player game will generally have all 100 artifacts scattered throughout the galaxy. Games with fewer players will have proportionately fewer artifacts (for instance, a 6-player game will typically have 40 artifacts, chosen at random from the full set of 100); and games with more players will have proportionately more artifacts. Furthermore, some games may have more or less than this standard ratio of 100 artifacts per 15 players, according to a random factor chosen at the start of the game.
When a game has more than 100 artifacts, it means that some of the artifacts will be duplicated. For instance, there might be two of the Key to Time, segment 2. If there are, than either of those artifacts will count towards the set of five--but you must also have specifically segments 1, 3, 4, and 5 in order to win the points for having all five segments. Having just a random set of five Key to Time segments that includes some duplicates isn't good enough. Similar restrictions apply to the other collectible groups of artifacts.
Whatever the number of artifacts in a particular game, there will always be exactly one Pandora's Box.