I’ve seen the full image. I think you’re underestimating the precision that can be accomplished by a talented artisan, even by hand, without fancy tools.

It would be well within the means of a skilled craftsman to make a sufficiently precisely patterned stamp or press to accomplish what we see in that image, especially given how thin that gold is (the article even says such artifacts are rare to find, since they “tear like paper”). All you need to make a perfect circle is a stick and string, or even just two sticks tied together. Scoring and then smoothing/polishing precise concentric circles into a pattern made of wood or stone wouldn’t be hard for a craftsman with metal tools, and if the stamp is precise, it will stamp a precise pattern into something so easily malleable.