I have six of these notes:
20 Dollars (Standard Chartered Bank) - Hong Kong – Numista
Three of them are dated 2014. They all look alike except that one of them has anti-Stokes fluorescence.
Here are two of them side by side under UVA:
Under UVC some elements turn yellow:
But…the strangeness involves the note with the E prefix. That note has anti-Stokes ink in the same distribution as the four vertical bars:
I checked all 36 of my Hong Kong notes and nothing has obvious anti-Stokes fluorescence like this.
There is a strange effect with three polymer 10 Dollar notes but the jury is still out on that. I think you will agree though…the green anti-Stokes fluorescence is plain as day on the 20 Dollar note. But only one note from one year.
Could this be a case of ink contamination? Why do this on one prefix and not the other?