If I was the kind of person who wanted to write a coded love letter, I would give the person I loved a copy of a much cherished book, identical in edition to the one I kept on my own shelf. I would write "17-1-1::38-9-1/56-15-14/57-4-22/1-1-4::19-6-21/69-6-5/13-7-8" on a piece of paper, slip it inside the cover, and hope they cared enough about me to decipher the code stored in the pages of a book written by someone other than me.