How to tell if a pen is hard rubber or plastic?

[amin]

I know this is probably a dumb question, but is there an easy way to tell?

 

My raw ebonite Danitrio smells like rubber, especially when rubber. My old Waterman doesn't smell as much, but I can tell from the oxidation that it is rubber. My dad's Conway Stewart Doctor's Pen, which I know to be made of chased HR, has no odor, even when rubbed.

 

The reason I am asking all this is that I am trying to figure out what year my Pelikan 100N was made. David Nishimura's description had said that the top part of the cap was hard rubber, the rest celluloid. However, the whole thing seems plastic to me. No part of the cap has a odor of rubber or looks discolored. Is there another non-destructive way to tell?

 

The other reason I ask is that I recently bought a "Big Red" Duofold from the 'Bay which was billed as hard rubber but seems plastic to me. How could I tell for sure?

 

Thanks all,

Amin