Is it still there. I lived in Montclair for a few years---light years ago!!!!
The REAL Claremont diner in Verona burned down in the late 70's/early 80's..."they" said it was a kitchen "grease" fire...and I suppose that is possible. As you know, nearly everything is possible here in NJ!
A new ultra-modern, steel and glass thing was erected on Route 3 West in Clifton called The Claremont Diner. I ate there once.
Best Regards, Julyman16