This section is from the book "School Needlework. A Course of Study in Sewing designed for use in Schools", by Olive C. Hapgood. Also available from Amazon: School Needlework: A Course Of Study In Sewing Designed For Use In Schools.
Page 126 consists of capital letters; page 127 consists of small letters and upright numerals; page 128 consists of small letters, suitable for fine material, and slanting numerals.
The material, thread and needle should correspond. The marking stitch consists of a cross-stitch taken over two threads of the canvas. To make the stitch, draw the needle through from underneath at the lower rig/it-hand corner of the square for the stitch; insert the needle at the upper left-hand corner, bringing it out at the lower left-hand corner; insert the needle at the upper right-hand corner, and bring it out at the lower right-hand corner of the next stitch.
Make no knots, but leave an end of the thread to be worked over with the first stitches, or it can afterwards be run in and out under the letter. Fasten the thread in the same manner. The stitches should all be crossed the same way; the thread should be fastened after finishing a letter, not carried from one to another. Have the back of the work look neat.
When marking on canvas is understood, fine material can be easily marked, by basting a piece of scrim over the place to be worked, and, after taking the stitches, drawing out the threads of the scrim.