http://www.w3.org/Amaya/ is a kind of reference browser from the W3C. The release history lists the first SVG support in Amaya 4.0 from 10 November, 2000.
Batik seems to be the most well-tested and conformant implementation of SVG at the moment: http://xmlgraphics.apache.org/batik/status.html, though I would use WebKit as reference because of it's market share and potential of Google and Apple to change the SVG spec.