Although my 365nm UV light does produce similar yellowish-green tint hotspot too, this is my first encounter for UV light with such tint.
Green tint is usually regarded as bad output for white LEDs, but i was surprised that K3 UV was able to illuminate embedded fibres and UV-fluorescent phosphors ink well across the entire length of the note. I also find green tint/ cast was more forgiving to my eyes, when i was inspecting the my other currencies.
Both photos are taken with same exposure duration, with beam direction from around 11 o'clock.
As usual with chinese flashlights, the design is nice but the emitter choice and user interface did not get much attention. How nice and intuitive would it have been, especially in this design, to have dedicated operating buttons next to each led? I know why they did not do it, one-button operation is cheaper to make, but the operation suffers bigtime.