specific names of the siglum used on SH

[Davidsch]

The answer depends entirely upon its function.
If it is a vocal indicator, then it would be a circumflex. These types of descriptions bring with them associations of vocal pronunciation.
If we assume it is an abbreviation symbol, then I don't think it has a name, but I would describe it as a macron abbreviation mark.

Of course do as you like, but for me "a macron abbreviation mark" is not exact enough.

If this was a replacement part for my car, I would like to know which part exactly we are talking about and 
for me the hook-above-facing-left symbol, (abbrev. hafal) on the Eva-SH, in the Voynich works.