It is too simple to be copyrighted since a 'check' contains no original authorship. Part of a series of different styled checks by <a href="//commons.wikimedia.org/wiki/User:ZStoler" title="User:ZStoler">User:ZStoler</a>
<a href="//commons.wikimedia.org/wiki/User:ZStoler" title="User:ZStoler">User:ZStoler</a>, <a href="//commons.wikimedia.org/wiki/User:WarX" title="User:WarX">User:WarX</a>, <a href="//commons.wikimedia.org/wiki/User:Gmaxwell" title="User:Gmaxwell">User:Gmaxwell</a>
Most of it was hand coded by me, the shape came from yes check.svg