UV color difference

[Shakey]

Thought people might find this interesting, a distinct difference between the UV stamp color of a 7 year old Partagas box and a 5 year old RyJ box. Both boxes came from reputable sources and everything else checks out. 

I wonder if HSA uses different inks or if something about the storage conditions caused one stamp to fade more than the other. 

[MrFolgers]

Interesting. Is your light focused more on one side than the other? What specific light are you using?

[Shakey]

It's a 365nm LED light, angled for the photo but that didn't change the reflected color. The RyJ stamp has a distinct blue color that is different from usual green.