A Thrilling Game of "What the Heck is This?"

At some point in our lives together, Robb and I realized that we shared the decorating sensibilities of ninety-year-old retired college professors. As a way of indulging our eccentric tastes, we go to a lot of estate sales.  It's fascinating to be given access to strangers' homes, and to get a glimpse of the objects they accumulated over their lives. 

Sometimes this is inspiring. Sometimes it's a bit sad. And occasionally, it's rather puzzling. 

This weekend, we brought home this mysterious object.  It seems to be made of an early form of plastic. 

Inside the body of this object, there's a metal mechanism. If the end of the mechanism is unscrewed, it can function as a plunger, depressing the "needle" within the barrel of the "pen."  The end of the "needle" never protrudes from the end of the "pen," but there is an aperture at the pointy end of the "pen."

The entire object is rather smaller and thicker than a typical early 20th Century fountain pen. 

Can you identify this item?  Do you know what the heck it is?