![](https://blog.des.no/wp-content/uploads/2015/05/IMG_9555-1024x683.jpg)
The #4 socket has visible corrosion (verdigris), while the #1 socket is almost pristine. The #2 and #3 sockets don’t look too bad apart from some dirt and deposits. Note that the #4 and #2 sockets seem to be made of brass or some other copper alloy while the #1 and #3 sockets seem to be made of steel.