The newborn princess wore a handmade bonnet by Irulea, a high-end Spanish children's wear and home goods boutique.
"Yes, she is wearing it backwards," Irulea owner Ayajo Villar tells PEOPLE. "The part that surrounds the face should be on the neck."
Whether the look was intentional or by mistake, the bonnet itself was a special gift for the new princess, with reports in the Spanish press that it came from the mother of Prince George's nanny, Maria Borrallo.
"We had contact with someone who wanted to buy some baby things, but it was all very discreet," says Villar, who owns the shop in the picturesque beach town of San Sebastian. "We don't know who she was. She didn't want to be seen or noticed."
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Whatever the identity of the mystery gift giver, she has excellent taste. (Villar declines to give the prices on the items, saying, "It seems to me very ill-mannered to say that about a gift that someone might have given the royal family.")
The bonnet "is extremely artisanal and handmade, the most handmade thing in our store," says Villar. "These items are not made as a series, not in a factory. No two are alike. We make them locally from wool in white and cream – we call that color bone."
"The person who bought the bonnet bought a set, which includes a jersey and some little slippers, all made from the same wool in the same color," she adds. "They bought various of these sets in both white and in bone, because she said she did not know the gender of the baby."
And no one was more shocked to see the little royal make her public debut in Irulea than Villar.
"It was a huge surprise for us when we found out that the Princesita Carlota was wearing our goods!"
For much more on Princess Charlotte's first days at home with William, Kate and big brother George, pick up this week's issue of PEOPLE, on newsstands Friday