I received this reply last year from Spain for King Juan Carlos's 85th Birthday.
The letter is by Bernardo de Lizaur, the current Head of Protocol. The only other birthday reply I have from King Juan Carlos is from his 80th Birthday. This letter has a almost identical message, but was written by then Secretary-General.
The letter says:
Palace of ZarzuelaMarch 1st, 2023Ms. Gertrude Alexandra Daly(My Address)The Head of Protocol of H.M. The King
His Majesty The King Juan Carlos has asked me, in his name, to send his sincere thanks, together with his affectionate greetings, for the warm wishes that, on the occasion of his Birthday, you have been kind enough to send.Upon fulfilling this request, I send a cordial greeting,Bernardo de Lizaur
