I received this reply a while ago from the UK. I had written to Prince Charles & Duchess Camilla to extend my condolences following the death of Prince Philip. While I had written to the couple, the reply is from Prince Charles.
The front of the envelope is the usual from the British Royals.
Wishing The Duke of Edinburgh a very happy 99th birthday! 🎊 pic.twitter.com/JDTwANrxra— The Prince of Wales and The Duchess of Cornwall (@ClarenceHouse) June 10, 2020
The inside right features a typed message.
The card says:
The Prince of Wales thanks you so much for your kind message of sympathy.
His Royal Highness has been enormously touched by the many generous messages that have been received in recent days; they have provided great comfort at this very sad time.
The Prince of Wales sends you his warmest thanks and best wishes.
The back of the card had a note about the photo. And includes the Forest Sustainable badge, which notes the paper is from a sustainable forest.