The front of the envelope looks pretty much like the others from the Monaco Royals. One thing that is interesting, is instead of left justifying my address, it is centered. And there are some other little things that make this different than Prince Albert & Princess Charlene's envelopes. Each office handles their own mail. So, sometimes, the formatting of the address is one way you can tell which office the reply comes from.
The stamp is of Prince Charles III of Monaco. And was released from 2018 to mark the 200th anniversary of his birth.
The postmark is to celebrate the Prince Albert II of Monaco Foundation. Monaco's post offices rotate through postmarks every few days. This postmark is one of the postmarks that we see every year, usually in December the week or two before Christmas. This postmark would have stamped on everything mailed in Monaco during the few days the postmark was running.
Inside is a lovely card. The front of the card features a wreath with a red bow, with the words "Best Wishes" written underneath in French.
Inside the card is a typed message and Stephanie's signature printed on.
The message is in French and English, and reads:
Best wishes for a Happy New Year
Stéphanie de Monaco