I received this lovely reply from the UK a few weeks ago. I had written to wish Prince Louis a happy 5th birthday.
The reply is the usual photocard for the Wales. The front features a photo of Prince Louis that was released by the Palace for Louis's birthday. The photo was taken by Millie Pilkington in Windsor.
The back of the card features a typed message.
The Wales have not changed their stationary since King Charles's accession. The coronet at the top of the card features the coronet of a child of the heir apparent, that William and Kate continue to use.
The message says:
Thank you for the very thoughtful message which you sent for Prince Louis' fifth birthday.
Prince Louis had a fantastic day, and your message was greatly appreciated by The Prince and Princess who send you their very best wishes.