Own work (a font version of this symbol is included at [1]).

Converted from a version of the following vector PostScript source code:

%!
300 396 translate 2.5 dup scale
/A{closepath gsave .6 setgray
fill grestore stroke}def/B{
[.1875 sqrt .25 .1875 sqrt -.75 0 0] concat
}def gsave .75 sqrt .5 scale
0 0 100 180 360 arc 0 50 rlineto
0 50 100 360 180 arcn 0 -50 rlineto A
1 setlinejoin 0 0 87.5 17 163 arc 
0 50 87.5 197 -17 arcn A
0 50 100 0 360 arc closepath
87.5 50 moveto 0 50 87.5 360 0 arcn closepath
closepath A grestore gsave
-61.26 -106.09 translate B
-15 -7.5 translate 40 -40 40 0 360 arc closepath
gsave 8 setlinewidth stroke grestore
5 setlinewidth .6 setgray stroke grestore
gsave 61.26 -106.09 translate
[.1875 sqrt -.25 .1875 sqrt neg -.75 0 0] concat
-316.53 9.1 translate .475 dup scale
0 0 20 112.5 225 arc 8 setlinewidth 1 setgray
stroke 200 sqrt 15 add dup 30 sub moveto
30 -30 rlineto 0 0 20 45 225 arc 45 -45 rlineto
5 setlinewidth 0 setgray stroke grestore
-61.26 -106.09 translate B
-15 -7.5 translate
40 -40 40 -59 -31 arc 8 setlinewidth stroke
40 -40 40 -60 -30 arc 5 setlinewidth .6 setgray
stroke showpage
%EOF