So this isn’t a double swirl either. Every card with a swirl can recreate this pattern under the right circumstances.
This is the same swirl pattern lit from multiple directions concurrently that creates the phenomenon of a swirl within a swirl. As you can see, the “tail end” of the first swirl stops before the “tail end” of the second swirl.
These are the main characteristics of every swirl: 1) when lit from one source of light, changing the angle of the card will change the placement of the swirl’s tail, and 2) when lit from multiple sources of light, the swirl’s pattern will show concurrently from each angle.
This phenomenon also creates “swirl orbs” when using a scanner or a multi-directional light source. For example, I used a ring light to take this picture which lights up the swirl pattern from 365 degrees (i.e., all angles). Because of this, the swirl is not as easily distinguishable because every “angle” of the swirl is lit at the same time.
Oh wow, I completely missed that! Sorry, please disregard my above message. I thought you were referring to the inside swirl, which I’ve seen named by eBay sellers as a double swirl countless times.
Haha no worries, when I stumbled upon the card ok cardmarket I had the same thought. It’s a super one-off card as it’s shifted over and clipped half way through
I haven’t spend that much time on this research I must say because there are just so much other things to find out aswell but whenever I think I see any possible weld line I have been screenshotting it. I do plan on making a good summary and explanation in a separate thread but I haven’t got the time to do it just yet. Therefore I make a quick summary of what I got so far but I actually have screenshots of lines that I think are different versions than these ones. So these seven examples are the different ones I have seen so far, not all of them create the nice looking double swirls but they are overlapping weld lines nonetheless. indeed the slowking (not nidoking ) picture @smokemon posted is the same as example 3
Edit: the way I try to recognize these weld lines in my search of needed data to confirm these things is I look for these interrupted orbs/ globes. Example of Moltres is one I spotted yesterday and still need to be compared to my made examples so I’m not sure yet Hat is going on. It just shows how I spot these things.
thank you! i have a typhlosion im getting back from psa soon that came back a 7. wish it had gotten a higher grade but it is what it is. Here it is before i sent it in.
Those are wickedly cool, very rare to come by doubles! Some of the older large holo faced cards can pop triples but it is incredibly rare from what I’ve seen.
It’s funny because in my latest PSA sub I have that double swirl lugia and two rayquazas from CoL
Both rayquazas have an identical double swirl that I just noticed they aren’t in any pleasant spots but still cool nonetheless. Makes CoL an extra awesome set
) picture 
they aren’t in any pleasant spots but still cool nonetheless. Makes CoL an extra awesome set 
