HELP!! How do these come off?

I  emailed you some photo's.  They pry apart with a screw driver and might break

 

Clem

Thanks, Clem!

I called the service guys at Atlas one time about those boxes. I'm not sure if the modern ones are identical to the ones on your older Atlas car, but they pry apart the same way and are very, very difficult to open without breaking. The guy at Atlas told me to just go ahead and break it and replace the plastic part, which is cheap and available separately from the coupler assembly.

Right. Then just replace the whole thing with Kadee coupler assemblies, that will NOT experience a broken knuckle as the older Atlas stuff does!