"Six" 72hp Roadster
As far as I am aware, there were only two model designations, the "4-40" (40 hp 4 cylinder motor) and "6-50" (50 hp 6 cylinder motor)*, each available in tourer, roadster or coupe configuration. I have this as a 6-50 Roadster, so I'm calling your answer close enough. The point is yours.
*I have also seen these referred to as "Model K" and 'Model S," respectively.