Dahlia identification

One year ago my family was given a very big dahlia bulb of unknown cultivar. I have splitted it onto three parts and planted three very (!) big dahlias (2 meters). The flowers are yellow, quite big (15 cm diameter), they remain sunflowers and are "vertical", I mean perpendicular to stem.
You can see photo:
I know names of all my dahlias and used to know names of all I plant in my garden. But this dahlia is complete mystery for me. Can anyone identify cultivar? Search engine on www.dahlia.org could not help to me because of lack of photos.
* Lukasz Komsta *
* http://www.komsta.net/ *
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