It's surprising some still say have tested even after the OP stated in the title they are counterfeits, and at 30% underweight not very good ones at that.
There are literally tons of these things floating around. I imagine most coins shops would have a basket full I know my local coin shop does, Ebay is full of them.
Some are a lot closer to actual weight too, here is just one example @ 26 grams. There are MANY sellers of these.

These can be bought for 2 bucks apiece. here
1888 Year United States Eagle Shape Silver Coins Ancient Antique One Dollar Replica Coin Feng shui on Aliexpress.com | Alibaba Group
If you check that link you'll see that a few "lots" were sold in the US, so buying from a US ebay seller is no guarantee of not getting one of these.
These guys also make them with real 90% silver too for a bit more money, and some will even put them in PCGS holders for you. Which BTW is why I'd never buy a coin in a coffin, that no guarantee. Just think if those guys can make a decent counterfeit coin, how hard is it to make a plastic box ? Being able to grade, and recognize this stuff is the best security.
Cool find, and honestly I wouldn't mind finding one, it would be a rush for a couple of seconds, which is about the same as any find anyway, because as soon as it goes in the pouch were off swinging for the next target.