Here is a quarter struck on a nickel from my collection. Michael K is 100% correct. When struck, though the nickel planchet fits and expands in the collar when struck by the 25c dies, it doesn't expand enough to completely fill it. Thus, you don't have complete rims. You will also see only partial reeding on the edge because only part of the coin is pushed into the reeded collar.
Looks like someone put a lot of work into a coin ring before figuring out they should be using a 90% silver quarter. How to make a coin ring.
