That’s a great question and the answer, quite frankly, is I don’t know.
I’ve also heard that FDR had a tattoo of his family crest. I believe it. I would not be surprised if more Presidents were tattooed, especially those Presidents who served in the military in their younger years, particularly in the Civil War and World War II.
It’s not out of the question to think it might be more widespread than we think. Many European monarchs had tattoos (King George V, King Edward VII, Kaiser Wilhelm II, Tsar Nicholas II), as did Winston Churchill.
This is definitely a question I’d like to find more information on.