This radio was undoubtably manufactured for Firestone by Stewart Warner. The same radio can be found with a Stewart Warner nameplate. The was the middle of the line radio for Firestone in 1936-37, a 5-tube model in a hand-rubbed walnut cabinet for $23.95.
My copy of this radio was acquired and restored in the summer of 2003. Click here for the before photo. I have only ever seen a few of these radios. Note how the center knob is different from those on either side in the ad! The knobs on my example are wrong.