[tempodox]

The mention of “U.S. currency” raises my suspicions. How does a canine distinguish between U.S. and Mexican or Canadian currency?

[nativeit]

Their handler whispers “dinero” or “money, eh” instead of “deutsche mark”.

[inglor_cz]

IDK about Canadian, but even I can tell the difference between USD and EUR/CZK banknotes by smell.

That said, no one on the Internet knows that I am a dog.

[JumpCrisscross]

Polymer versus paper?

[b112]

Polymer versus cotton + dyes. US currency has a unique smell to my human nose, even.