Thomas hasn't been on the site since the cryptic post on Friday. I don't think he'll be back, since he's got it all figured out! Lol!
A silver dime planchet weighs 2.5g so the 4.3 gram has nothing to do with it. And, if you lay a dime on top of a nickel you can see why you would get little or no rims. Some people dismiss old threads, but the current people can still discuss them.
I found one like hes describing it weighs 4.2 but mine says 1962 D but its really hard to make out the words under magnification
Simple. A dime planchet (raised rims) is struck by quarter dies. The rims don't disappear they just flatten a bit sometimes, but not completely and not evenly.
A coin die along the outer edge has an incused/recessed circular ring called a 'gutter.' It's job is to sharpen the rim upon striking.