Both are grammatically correct. After the word پول, there is an unwritten sound stuck to ل,(similar to A as pronounced in the phrase " a book") called KASRE or کسره in Persian which functions like the word OF in English language as it is used in the phrase "the leg OF the door". Thus we can say, it conveys a sort of possession similar to that of مال in the second sentence which eventually makes the two sentences somehow equal.

Both sentences are correct and sound natural :)

hi, both are correct and sound natural to me. I also add another phrase: این پول کدام کشور است؟

Thank you all for very helpful answers! I appreciate you taking time to write the examples and explanations. Jacob

Hi Jacob Both are natural to me, also you can say این واحد پول کدام کشور است