Roman Hexagram, Guilloche Style

Guilloche is a decorative border made of interlaced bands Guilloche

Compare:

http://www.flickr.com/photos/gbertoia/65412054/

http://www.flickr.com/photos/zeevveez/2671093798/

http://www.flickr.com/photos/geo1001/257660122/

http://www.flickr.com/photos/imagicweb/397529580/

http://www.flickr.com/photos/triptorome2006/3490393633/
http://magendavidalbum.blogspot.com/2009/10/blog-post_06.html

Picture was taken at El Jem museum, Tunisia. Courtesy of ajhammu0 / Andy from Flickr.
Beginning of third century. At the centre an hexagon, in the middle of which a cruciform flower which indicates that it belongs to christians.