Dunn is one of those "small high quality makers" that collectors learn about once they get beyond Parker, etc (hey, I've never gotten "beyond" Parker, but I'm stunted).
I'm not a Dunn scholar though my recollection is the company lasted about three years 1921-4 or so, killed by a worker's strike, not by bad product or by bad sales. They had clear-barrel pens years before Parker or Conklin. And that famous (casein?) red butt. And, their pens were good. Not a "third-tier" maker, just small. I've had the pleasure to shoot the personal collections of two of the most active collectors (at least the two most active "known" collectors... who knows what lurks out there?) of all things Dunn.
One of the big names in Dunn pen models was the Dunn Camel. But the notion of the Camel transcended pens for the manufacturer.
Here is one heckuva Dunn Camel (or is it a Dreadnaught?)
It is resting on... A Dunn Camel.
Vintage pen eye candy no doubt.
regards
David