Identity And Value Of This Old Fountain Pen Inkwell

[schnorg]

This probably goes with the Eagle Pencil Co. fountain pen I just posted.

 

I cannot identify this item. I'm guessing it's roughly 100 years old, but can't be sure.

 

On the reverse, it has two markings:

one says "No 4"

one says "RD505078"

 

I'd greatly appreciate any input on its identity and value.

 

Thanks!