Testing kitchen knives with lead swabs

Dear enthusiasts, while I've seen posts related to testing knives for lead content I wanted to share my experience using cheap testing cotton swabs from amazon (do not buy) using water.

The knives are:

1. Shiro Kamo Hocho, Bunka
2. An old Wüsthof bought when Kaufhof was still a thing in Germany, then heavily misused
3. ~10 year old Opinel Carbon
4. ~3 year old Opinel Inox
5. cheap chefs knife from Amazon
6. 8 week old Gränsfors Bruks splitting hatchet

I was very concerned having a positive test on the 1. Bunka. I then tested more knives (more than in the pictures), until I figured out with the two Opinels that the test seems to always turn purple on carbon steel. Inox was always fine. Hatchet was only gray, not purple (I know, it looks a little purple but it's just gray).

I since learned that those sodium rhodizonate/sulfide tests seem to be rather unreliable on metals (they may be good for testing wall paint) from this sub and other sources. Unfortunately, as you can see on the packaging picture, the explicitly state they work on metal. But, I trust Opinel more to not make knives with lead in them than a random chemicals company from Guangzhou (that's where the packaging label sais the tests are produced). The Bunka is also from a known distributor in my town.

So for now, I'll not buy random knives on the internet but I'll probably keep using my Opinel. Or can anyone out there guide me in a better direction on testing knives for lead that does not require expensive laboratory equipment to perform XRF testing?

Cheers and thank you.

Note: I'm NOT a professional in metals nor chemistry. Especially chemistry is black magic to me. Do not take my advice.