Just missed out on a 4-pac of Williams L&N 2-bay hoppers.  Didn't even know they existed until this week.  Does anyone have a part number or set number?  Means a lot to me and my model railroad set as I'm originally from Louisville and my mom was a passenger agent for the L&N.  How old would these be since currently W by B only sells quad hoppers?  How rare are they?  Typically speaking, would I ever be able to find hem again?