Mass card

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A card sent usually to a bereaved person or family indicating that the sender has arranged for a Mass to be said on behalf of the deceased.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Christianity A religious card that states that a Catholic Mass has been said in honour of a dead person, or as a request for special favours such as improved health or success in a worldly endeavour.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun (Roman Catholic Church) a card sent to a bereaved family that says the sender has arranged for a Mass to be said in memory of the deceased