Real or fake (Ming dynasty cash coin)?

Hi, 

I'm relatively new to numismatics, and I recently bought the following coin:

It was sold to me as a Ming dynasty cash coin from circa 1630-1644 (more specifically, Hartill #20.292) at a relatively inexpensive price. However, I've read recently that there are a lot of fake cash coins, and now I'm scared 😅 Especially considering its Numista rarity index of 85 (I know that this does not necessarily reflect the actual rarity of the coin, but still). Also, there seems to be this sort of small “crack” on the bottom of the reverse side that got me thinking. I don't know if brass can crack like that or not, and I only noticed this after buying the coin.

Do you think that this is real or fake?

Your photos altered for clarity so an expert can better assist you. Meantime can you provides weight and diameter?

Thank you for your help, harryg!

The diameter is approximately 24mm. Also, I tested and the coin is not magnetic.

I don't have a precision scale with me right now, so I can't provide a very accurate estimate of the weight (sorry). I tested with a kitchen scale, and its reading seems to fluctuate between 3g and 4g, but I don't know how reliable it is.