[tgbhu]

Taiwan? Why don’t they suspect N Korea?
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It's not a suspicion, even Taiwan's media reported that with complacent, Taiwan has made fake RMB for 2 decades.
I'm Chinese, your words remind me NKorea, I heared only Switzerland can make an ink used for USD cash, does NKorea have the tech to make it?

[null and void]

Dunno. The only reasons I think of N Korea is that they are well known to be in the counterfeiting business, at least of US$100 notes, and they do have a longish border with the PRC.

As to where our ink comes from? I don’t know that either.

I don’t think it would be beyond the ability of a nation state to duplicate a recipe. Or perhaps bribe/blackmail someone who knows it.