Chinese Large Cash - Probably Fakes?

I bought a few large cash on ebay because (1) for a couple of bucks, they make nice paperweights, and (2) I was interested to learn more about the fakes that are out there.

I would be interested to discuss with others and learn more about how to spot a fake, other than the obvious "don't buy coins from China". I also have a presumed genuine one here, so let's compare.

Here are my descriptions and impressions of this bunch:
1. 45mm / 3mm thick. Bought from ageshang1573 (8/2023). Looks like an obvious fake, with red paint. Blackening of fields doesn't look natural.
2. 52mm / 4mm thick. Bought from ageshang1573 (8/2023). Obvious fake - the fields look like my oil-rubbed bronze bathtub faucet.
3. 49mm/ 4mm thick. Bought from tshangfu2022 (8/2023). Assuming this is a fake, someone put a little more effort into it. The tone is uneven, the characters look worn, and the patina doesn't scrape off easily.
4. 54mm / 5mm thick. Bought from anhuijieshou2013 (8/2023), who has been called out for selling fakes in another thread on here. This one is nice and heavy with high relief. There's a little bit of dirty encrustation which can be scraped off but not very easily. To me, the characters look a little blurry. If it's a fake, they put some since effort into it.
5. 59mm / 3mm thick. Bought from tshangfu2022 (8/2023). Some dirt, which comes off easily. The rim and characters don't have the brassy tone, contrasting with the fields, that I'm used to seeing. Could this be genuine, or is this the effect I'd get if I buried my oil-rubbed bronze bathtub faucet in the yard and dug it up a few weeks later?
6. 56mm / 3mm thick. Bought in Oxford, UK in 1995 at an antique store. I assume this one is genuine, at least it predates the era of ebay fakes. But I would still like to learn more about how to distinguish this real one from the best fakes. The shape is slightly irregular and the texture is different from the others.

I'm interesting in hearing others' opinions on these. Others besides me are bidding and buying these on ebay, so hopefully this post can help to educate some folks, beyond the obvious wisdom that we should buy from a reputable dealer if we want more than just paperweights.