A family of four lives here?

The 20 + C + M + B + 04 is supposedly a reference to
Casper, Melchior, and Balthasar,
The Three Wise Men.

Every year (in this case 2004) about New Year's
people dressed up in costumes visit homes to collect food and other items
for the not so well off.
The markings over the door mean this family made a contribution.