This code was widely used in the 1970s, but is much less used today. (The terms bandana code, hanky code, or flagging are much more widely used among those in the leather subculture than the term handkerchief code.) It should be noted that this code has come into more general usage today.
Generally speaking, solid turns to a liquid at its melting point. Ice turns to water at 0 degrees Celsius. Chocolate melts at 25 degrees Celsius- Yum! Ice (solid) thaws when the temperature rises above 32 degrees Fahrenheit, becoming water (liquid). Other solids (oddly) vary. Generally speaking, solid turns to a liquid at its melting point. Chocolate melts at 25 degrees Celsius- Yum! Ice (solid) thaws when the temperature rises above 32 degrees Fahrenheit, becoming water (liquid).
If you measure liquid temperature while distilling, you may have noticed that liquid temp can often be much higher than 174 before a still starts producing. Again, the boiling temperature of a solution that is 100% ethanol is 174 degrees.