How long ago were those books printed? Threads nowadays don't have weight on them. I just checked a brand new spool of Coats and I guess that 457m would be comparable to 50 weight. These new snap up spools usually have a bit of loose thread, you can feel this to see if this is a good weight to use. If you're machine appliqueing use a color that matches your work. Hand applique, YLI 100# silk is great. YLI can be ordered on line.