Well it clearly has nylon bristles, but I'm guessing you already knew that, eh?
Honestly, my guess is its just a nylon brush manufactured here in the US at some earlier date by some company. Ever-Ready and Made-Rite were probably two of the more well-known manufacturers, but hardly the only ones out there. Other than that about all I can tell you is that it had to have been manufactured sometime after 1938, as I believe that was the first year nylon was introduced to consumers in the form of nylon bristled toothbrushes.