1) Arcade high score entry 2) Authorization, at times 3) First letters 4) First letters of words 5) Hanky embroidery 6) Letter heads 7) Monogram 8) Monogram parts 9) Monograms 10) Personal letters 11) Signs a memo 12) Some tattoos 13) Tree carvings Found on https://www.crosswordclues.com/clue/initials