It really does look more like the archimedean spiral, than any other. In all drawings I found, the archimedean spiral starts at the pole, while the equiangular spiral never reaches the pole. In the logo on the tie, the spiral quite clearly starts at 0.
Thanks a lot rcgldr and the other for help...
Thanks for the comments! I just don´t really think it´s the Golden or Equiangular Spiral as the angle to the rightmost slope to the x-axis seems a bit too steep for it to truly match.
Sure, it´s an embroidery and geometric accuracy cannot be fully expected, but I remember the guy telling...
I met this old nerd wearing a tie with a certain spiral, which does not look like a Bernoulli spiral to me. He actually told me, what it was, but I seem to have lost the note and time made me forget it. I wouldn´t be able to describe properly, so I have a photograph of the tie on my flickr...