I am interested to know how the background blur in this image was done. Is it a petzval lens?
It could very well have been taken with a vintage petzval lens, however there are many other lenses also capable of creating a similar swirling Bokeh effect as you see in this image. Ultimarely it is unlikely that you would be able to tell for sure which lens was used without asking the photographer.
Here is a list of a few other lenses that are famous for creating the "swirl"
Recently a kickstarter campaign raised the funds to recreate Petzval lenses with modern mounts: http://microsites.lomography.com/petzval-lens/ Though they are not shipping to the public until June 2014 so I imagine that it is unlikely that the shot you linked was taken with one.