my neighbor is a visually-impaired quilter who when she learned her vision would get no better only worse, she learned Braille. Her daughter used French knots in the quilt made for her. Of course she has done this over many years but it's also how she also labels them. Often the knots are the same or a shade lighter or darker than the fabric they are embroidered on. Just a short message with his name in Braille will let him know it is his also. You can Google the Braille alphabet. You could just put his first name or initials.