Socket Head Strain Hardened (although this is usually just H when referring to sheet metal)
I have also seen some use of Semi Hard in place of Half Hard
ASME Y14.38-1999, "Abbreviations and Acronyms" lists the following for the abbreviation "SH":
Drawing Text Term
SH SH scleroscope hardness
SH sh shackle
SH sh share
SH sh sheet
SH sh sheeting
SH SH shield [electronic device]
SH sh shower
SH sh shunt