Questions about defects on Chinese Warlord Era coins

Goodday!
I just bought this coin and I understand that they didn’t always have strict standards for metal composition. Is it normal if a bit of yellow metal shows through in some areas(all Features right except weight, 5.44 on mine cheap 
scales)?  N#22630

 

And another question about these 'lines': I’ve seen them a few times on coins and I’m wondering — are they caused by something external, or from poor condition of materials and mint?    N#28945

Can somebody please tell me about this? And if possible, could you also share information about other defects you have seen on Chinese Warlord Era coins?
Thanks!

Hi there, yes this is common and purities and size can vary wildly on this era of coinage and sadly because of this fakes are abound (yours is fine)

Thanks!