The RSVP card is a paper note in the Fallout 76 update Wastelanders.
Background[]
The note is an invitation to Penelope Hornwright's 29th birthday party, sent to Daniel Hornwright. It is marked with the reply "unable to attend." This card is related to the quest Trade Secrets, listing the date of March 4, 2048, a clue to the password needed to access the safe room (030448).
Location[]
The note is on a bar countertop in Hornwright Estate.
Transcript[]
The pleasure of your presence is requested for the 29th birthday of Doctor Penelope
Hornwright on March 4th, 2077.
Daniel Hornwright