Since the major update that removed gameplay-altering item set bonuses, a calling card is now left behind "when a player is killed by another who is using a specific item set."
This sounds simple enough, but are there any specifics, i.e.,
- is a calling card dropped only when killing using a weapon in the set, or with any weapon?
- is a calling card dropped even if the death was feigned by a Spy using the Dead Ringer?
Or is a calling card always dropped?