Basic abstract equal-armed cross design with circle at center and surrounded by 4 nails.
Called a "Coptic" cross by Rudolf Koch in his The Book of Signs (Dover); may not be prominent in Coptic Christian symbolism in this form.

Apparently sometimes the arms of the cross extend through the circle (dividing it into four quadrants).
Based on out-of-copyright design by Rudolf Koch (died 1934).
Vector version of original PNG Image:Coptic-Cross.png, which was a quickie image to fill a gap in the Cross page. PNG was copied to Commons from en:Image:Coptic-Cross-so-called.png (uploaded on 17 October 2005).
Converted to SVG from the following vector PostScript source code:

%!
4 dup scale 6 setlinewidth
10 75 moveto 50 0 rlineto stroke
140 75 moveto -50 0 rlineto stroke
75 140 moveto 0 -50 rlineto stroke
75 10 moveto 0 50 rlineto stroke
75 75 15 0 360 arc stroke
75 75 translate
/a{1 setlinecap
-35 -49 moveto -49 -35 lineto stroke
0 setlinecap
-42 -42 moveto 20 20 rlineto stroke
-24.24264 -24.24264 moveto
4.24264 0 rlineto 0 4.24264 rlineto
-4.24264 0 rlineto fill}def
4{90 rotate a}repeat
showpage
%EOF
AnonMoos (initially-uploaded vector conversion by Erin Silversmith)