Very cool.

Steelies are great!

Yes, the '4' is almost gone. This is a 'struck through grease' error, and adds a little value to the coin. During the minting process, hard grease fills the die, and the pattern disappears. Mint workers are supposed to clean the dies to prevent filling, but sometimes they miss. Thanks for sending your pictures.

You can see more examples, and more explanations, on this page:

https://coinquest.com/cgi-bin/cq/coins.pl?coin=1422