I found that working with copper and brass, you can take a spoon to a quarter, tap on the edge, and over a few hours of tapping mushroom the edge of the coin. The same is true if you're nozzle ever slams into the print bed during adjusting the Z height and fine tuning the Horizontal Radius. It does touch the bed, so you're 0.5 nozzle setting, just shrank. This can lead to the delamination of edges of printed parts. Fudge it for Slic3r and nudge it down to 0.49, check for delamination, then step it down again if it still leaves gaps if it's not right on, and you're factory 0.5 nozzle, changed diameter, you'll notice gaps between standing layers.
With the quarter, you can make a nice ring, if somebody can carefully cut out the middle because, you'll still be able to read the edges on the inside of the ring. Even silver dollars are good for that. You can see what I mean here, where I pulled it apart.
